Archive for the ‘Lecture Notes’ Category

Joe Jordan led us on a glorious tangent filled romp through the sky — chasing rainbows and other phenomena with photos, chalkboard drawings, and props.

Joe, former physicist NASA, current director of the Sky Power Institute (http://www.sky-power.org) talked to us at the Randall on November 20th, 2014 about all manner of sky phenomena and the physics behind them: the complexities of rainbows, sun dogs, sun pillars, moonbows, haloes, glories, contrails, green flashes, castles in the air, the directionality of meteor showers, and more!

A lot of what we see looking up, or what we see downwards looking out of a plane is the result of ice crystals in the air, their orientation to the sun, and the observers particular perspective.

Sun pillars for instance — where a column appears to rise from the setting sun — is sunlight reflecting off the undersides of ice crystals. It is the same effect as the sun reflecting off the waves toward you, just in the sky. Other effects depend on the angle that light is hitting the crystal, and where that crystal is in relation to the light and you.

A more complicated phenomena, but one of my favorites, are glories. Sitting on the shadow side of the aircraft — as you are coming into land and passing over clouds, you might see a glory in the clouds, a circular rainbow. At the center of that you might be able to make out the shadow of the aircraft.
(If you are a SCIAM subscriber you can read more at http://www.scientificamerican.com/article/the-science-of-the-glory/)

Joe talked a fair amount about the appearance of sun rays fanning out. Sun beams are essentially parallel given the distance the travel from the sun. The fanning out is an optical illusion akin to how train tracks look when we look down them.

We spent the longest time with the intricacies of rainbows, the bending of light through raindrops and how that gets to our eyes. Multiple bounces leads to double and triple and more rainbows (in the lab, this has been done up to the 15th order, but in nature you’d be lucky to see a 5th order rainbow).

My favorite factoid of the night is that although what we see a rainbow as a static thing up in the sky, what that rainbow actually is is an animated mosaic projected onto our eyes — millions of rain drops bending light in our direction, changing colors until they fall “out of the picture.” followed and replaced by the raindrops above.

Double Rainbow!

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(notes by Joel) Geologist and plate tectonics animator Tanya Atwater spoke to us October 16, 2014. She gave us her presentation called Living in the Plate Boundary and Through the Ice Ages.

The presentation was largely based on diagrammatic animation videos which these notes cannot describe. But you can see them yourself on Atwater’s website  (or you can Google Atwater animations). I apologize that I wasn’t as able to take notes as usual since my eyes were up on the video screen a lot.

The surface of the earth is made of plates floating on (and diving down thousands of miles into) the earth’s molten mantle, which is always flowing.

When you look at the animation of the continents coming into their present formation, India seems to move faster than the rest. This is partly due to the size. Smaller means it can move faster. Of course the speeds are all pretty slow, taking many millions of years. (Speeds are similar to how quickly a fingernail grows, according to Julian’s talk back in July.)

The Himalayas are uplift (crumpling and wrinkling of the plate that pushes the surface up). This is due to the direct-hit crunching of the Indian plate against the plate to its north.

The Pacific Plate is the largest plate, taking up almost 1/3 of the surface of the earth. It’s being dragged past the North American Plate to the NW, scraping against it and at the same time leaving bits behind along the edge.

The area west of North America has been for a long time (until recently) made up of three ocean plates. Ocean plates are formed by spreading mid ocean rifts where mantle magma wells up in the gap. (Continental plates are formed by uplift, by volcanos, by wind and glacial deposits, etc.) The two plates on the east side of the rift zone have flowed under the Americas now (a process called subduction). There’s a tiny bit left of one (Juan de Fuca Plate) in Oregon and North California Coastal waters and a little (of the Farallones Plate) near Central America.

As the rift spreads, the Pacific Plate gets bigger on its east side faster than it moves northwest. That means it grows and seems to come closer while in fact it is moving away. The direction of movement is not directly away, but scraping NW along our coast, pulling our coast out and stretching the North American continent. That’s why the high areas that used to be Utah and Nevada had room to collapse and fall over becoming the basin and range provinces with lots of gaps between high ridges. It’s also why the Gulf of California has opened up.

The San Andreas

Tanya’s graduate thesis was to try and figure out the San Andreas Fault, which turns out to be a unique fault over the whole earth.

If a slipping fault is a perfect line in the direction of slip, it has no gaps or places that push against each other (forming wrinkles, i.e. hills). But in reality, all places have some kinks, so there are hills and gaps formed.

Pinnacles Park in California has a very different kind of volcanic rock. Rocks the same have been found hundreds of kilometers away so we know that one side of the slipping fault moved that far since the eruption.

Bodega Head has granite that has moved up from Southern California, 500 km, as do a few other spots on the Northern California coast.

About 25% of the motion of the fault’s energy is spread into the Tahoe region in smaller stresses. In 10 million years, there will be an ocean alongside Las Vegas, because the Pacific Plate will have dragged what is now California away, probably.


Before the San Andreas, we had a subduction zone as the ocean rift pushed plates under us. The mid ocean ridge where the spreading areas were is now mostly under us. A subduction pretty much has to be along a straight line. When the subduction hits the melting point (not from friction but from the internal heat of the earth) it bubbles up through the plate above it. That is why there are volcanos in the Cascade Mountain Range. It’s the Juan De Fuca Plate coming back up. Some is trapped under and that becomes granite. Some makes it to the surface and is lava. That lava flowed to the coast and was crumbled and tossed into a mixer of rocks, seawater, etc, some of which was dragged back down by the subduction to enter the whole cycle again and again. Meanwhile, some of the rubble of this cycle is left on the edge of the North American Plate. This is the accretionary wedge.

Other geographical features

The Great Valley (a.k.a Central Valley, San Joaquin Valley, etc.) is the collected debris of the volcanos and cycles of subduction at the edge of the continent. The land west of it (the coast range) is the uplifted part of that debris (cause by bends in the slipping fault pushing mountains up) mixed with melange of things dragged along from elsewhere. The melange is blue schist and chert and all sorts of stuff.

The Transverse Ranges (Tehachapies) that curl toward the coast are granite like the Sierra Range, but the farther south you go the more deeply eroded it is, so the farther under the formation you are looking. The granite in places like Joshua Tree Park are not smoothed into canyons like the Sierra’s because there were no glaciers to scrapes and smooth them. They formed rounded boulders instead.

The L.A. basin is deep and filled with mud.

Between Santa Barbara and San Diego there was a break and a gap opened. The land that was there got pulled and rotated. It is now the block of material that the Channel Islands and Santa Barbara sit on. It tumbled and was rotated to its current position by the two plates grinding past one another within a gap where the coast was pulled out allowing for rotation. Geologists can tell this is so, even though it is unlikely, because the rocks formed with their magnetism lining up with the poles. Now it points east in all those areas, so they know by paleomagnetism studies that the whole section pulled apart and rotated.

Ice Age

The present sea level is about as it has been since the last ice age ended 6,000 years ago. It’s melt from the ice age glaciers. The maximum of the ice age was about 17,000 years ago after tens of thousands of years of ice age. We are now in an interglacial period. The previous one was about 100,000 years ago, and they happened in the past about every 100,000 years. Ice ages always come on slowly and end quickly.

As the glaciers melt quickly, the sea level rises a lot. (For the most recent, between 300 and 400 feet all around the world at once.) Each place where a sea level remained a while, the wave action cuts a terrace on the edge of the continent. By the time the sea level goes gradually down and then quickly back up the next time, the continent has risen some distance, so the next wave terrace is below the old ones. This eventually forms a stair-step coast line. The older steps are more eroded but they are highly visible even to the untrained eye.

If there is a lot of sand in the waves, it takes up the wave energy, but if not, the energy cuts new terraces.

There was so much more she said!

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(Notes by Joel)

John Scarpulla talked to us September 18th, 2014, about the Living Machine at the Public Utilities Commission (PUC) building SF Headquarters. John is a project manager, not an engineer. Very informative.

PUC headquarters: a well built building. Safe place in a quake. Command center for emergency operations. Features: Rainwater harvesting in preschool play area made of spongey material that’s permeable. Collects the water there and uses it to irrigate street trees.

The system called the Living Machine, a million and a half gallons per year. Not a large project compared to the 65 million gallons per **day** that the SF sewage treatment plants treat, but an example, a demonstration site. And a chance to test processes, including permits and ordinances. Wastewater treatment out in the open. Integrate technology into the neighborhood providing green in tenderloin.

Building is separately “dual plumbed” for potable water from the Hetch Hetchy system and wastewater internal system.

Water flows from primary tank to flow equalization tank to wetlands to building in a 48 hour loop. Flows from 7 to 7; none at night or weekend. Wetlands are in sidewalk, lobby and then the water cycles through the basement systerms.

Primary treatment tank is called and looks like a big “hotdog” and they needed a permit for that because it goes under the sidewalk.

First, a trash chamber separates things that shouldn’t have been flushed.

Second, a settling chamber removes a lot of the settleable and floatable solids. The solids are processed elsewhere. They don’t manage solids on site because the site’s too small.

The cycle is in waves, sending batches into the system with a 3000 gallon equalization tank. Recirculating tank for water available to go back to toilets is 6000 gallons. Wastewater treatment of 5000 gallons a day.

Nature wetlands, etc. process water by slowing the flow and cleaning the water but this speeds it up while cleaning it.

One way they do that is with “tidal” action. Water fills and then goes down like a tide every 58 minutes. Process quickly because the plant roots and soils are exposed to an influx of oxygen when water is low and organic microorganisms when the water is up. Most of the solids that were suspended in the water are removed by this process. Both aerobic and anaerobic bacteria involved. Self sustaining.

Ramped up population at the beginning, two years ago: Plants got inoculated then synthetic wastewater (milk solids and ammonia) were fed to it until real nutrients came into the system when building opened. Gradually reducing synthetic wastewater as human use increased so microorganisms kept stabilized.

Off gassing of nitrogen tells what population of microorganisms is like.

Department of Public Health (DPH) required wastewater to stay six inches below topsoil, so there are overflow vents to the sewer system preventing sidewalk overflows. Four inches under there’s a mesh to keep people from digging into the wastewater. No odors because subsurface vent sucks in and odors are emitted through a rooftop carbon filter scrubber.

Reasons particular plants were picked: Marsh plants can stand water in their roots all day every day. Must be tolerant of high nutrient levels. North side gets no sun. Plants have to be able to survive those conditions.

Landscape architect new to this but experienced engineer that has done this system before.

Batch sizes depend on whether it’s raining and day of the week. People are not in the building weekends.

Golden Gate Avenue side is the tidal flow wetland. Polk is the vertical flow wetland: one pass through of the water there first to cell 2a, then down hill to cell 2b. Light tan tint to the water after going through the wetlands. The filtering is then complete so it goes into the interior lobby plants which are a different plant pallet with species that like more sun.

“Acre Café” is in the lobby area twenty feet from the treatment.

There are pumps in addition to gravity. Twenty percent of California’s electrical and 30 percent of natural gas in the state is used for water systems. Living machine uses 75 to 90 percent less power than other systems available because they all use force through a membrane and this does not.

The water gets disinfected with UV light and a little chlorine in tablet form like a pool before it goes to the toilets again. There is one building in Toronto trying something similar that decided not to do chemical treatment and the mold growth became a public health and operational concern.

The system is entirely operated by computer from control room or from desktop computer or smartphone. Fully automated.

Aqua Nova specializes in wetlands.

DPW (Public Works) was involved because it was a large public building being built. Permits: No regulatory rules existed for this so they had to create some. DPH and DBI (Department of Building Inspection) and PUC signed letter of agreement. Will test yearly and inspect plus send results to DPH. Choloform, Turbidity, Oxygen load, etc. In the system itself, sampling is the biggest time draw. Otherwise little for humans to do to maintain it, oh except: Maintenance is big because warmth attracts sleeping, then there’s vandalism. People steal the plants and they have to be replaced.

Inreach wasn’t done as well as they wanted. For an agency of 2300 only about a dozen people came to the one inreach meeting. Outreach was good though.

Project purpose: help ask How can we get other building designers to rethink? In large residential, about half is nonpotable. 95 % in commercial buildings.

City ordinance introduced: Now any building in SF can reuse blackwater, graywater, stormwater (hits ground), rainwater (hits roof), or groundwater.

Amended an ordinance: Buildings can now share non-potable water between them but only by contract, whether paid or free.

If you go into the sidewalk you need a “minor encroachment” permit and it street then “major encroachment” permit.

PUC’s nonpotable guidebook is available from John. Grants from PUC are available for certain sized buildings to encourage development of more such systems or similar. If you expect to offset enough per year you get the grant.Moscone and Transbay and others will use from groundwater systems on sumps. Sump water doesn’t need all the plant cycle stuff, just filter and UV.

The Bullet Center and two military systems in San Diego are using black water, otherwise most systems that exist now are sump (groundwater) or storm water.

John Todd is the inventor of the living machine and calls himself an ecological engineer.

AAA Clifornia Automobile Association building had a groundwater system but was a failure due to high iron in the water. (Different locations have different minerals in groundwater.) gave them orange toilet stains so they only operated it a month. Redid building and took the system out.

In PUC building graywater and blackwater both treated combined, so it all is called black water.

Gray water reuse for homes was allowed as of last year by state law changes. Became okay for using indoors in January 2014.

Airport has a hidden and fenced-in staff building that does the same full system for blackwater but only 475 people work there.

Solar panels produce 12 percent of the buildings energy and the wind turbines 1.5 percent so easily covers the system pumps and UV.

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Spreck Rosekrans came to us August 21st, 2014 to make the case for restoring Hetch Hetchy from reservoir to valley. The dam just passed its 100th anniversary in 2013, but what was hugely controversial at that time (more than 200 newspapers opposed, and John Muir famously broken-hearted by the decision) is now something of which most San Franciscans are proud.

Spreck spent only a little of his time on the “why” of making the effort. We lost this special place, and many people regretted the choice to dam it at the time, and today we have a chance to correct that mistake and restore an iconic place. To do that would show not just values, but also show that we can make meaningful water reform (not something that seems to come easily to Californians). The arguments (which Spreck also layed out) against it are many — people feel that the water is SF’s birthright, that Hetch Hetchy was a swamp, that we are actually protecting the valley, and there’s hydro power from the dam, the cost of removing it, and that we need more storage not less.

The main thrust of the talk was on the practical question of: if we removed the dam, how would we actually supply the water coming into the pipes of the 2.4 million people? It is not a pie-in-the-sky, wishy-washy notion as one might first think. EDF hired 2 mainstream engineering firms, and one law firm to look into what it would take (this resulted in a publication called Paradise Regained — the summary on this page gives a pretty good idea of what is proposed).

The amount of water involved is not the biggest. Of 5 big water projects over the last 22 years, Hetch Hetchy would involve less water than 4 (Delta ESA work, Central Valley wetlands, Trinity River, and rivers in the Central Valley). It would mean juggling water from various sources, doing what is known as “water banking”, taking more from the Cherry reservoir. Looking at the dry years, that kind of work (with the removal of the dam) would get is to around 80%.

The last 20% would take working to be more efficient with the water we have, from farming practices, to recycling, to just plain using less. These are things that of course are not easy, but they are things that we can do — and given current state of our reservoirs maybe things we will have to do anyway. At the end of the day though, we could have our cake and eat it too.

Hetch Hetchy left alone will be with us a long time – unlike other dams, silt does not seem to be a great problem there. Choosing to restore the valley to its former glory would no doubt have its complications and difficulties, but that choice is not just a fantasy.

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Julian Lozos came to talk to us on July 17th, 2014 on measuring earthquakes – how they are taken and how they are used with an important distinction between measured and calculated data.

Corona Heights where our Randall sits has very visible evidence of an earthquake. Julian referred to the fault on the side of the hill as a “slip & slide”. It is very rare to be able to see one so exposed — you can see the polish from the pressure and the striations showing which way the surfaces slipped relative to one another.

After a quake, we want to know where was it? How big? Will there be aftershocks? The audience was invited to weigh in on what questions come to mind immediately after feeling a moderately small shake. It turned into a long, interesting discussion. Tsunami turn out to be a low risk in the Bay Area due to distance from faults that cause them. One at north end of the San Andreas (“triple junction” zone) can produce tsunamis but they come at an angle that diminishes them. Northern CA and Oregon north would be hit hard. In the Bay Area, only a landslide displacing lots of water would cause a tsunami. The 1906 SF quake caused a one inch tsunami.

Another way water can be a problem is seiching–water in a basin sloshing around to the point of generating dangerous waves. This would not happen on the Bay, since it’s shallow, but it might be a problem in Lake Tahoe.

Bigger quakes get named, even though the names are often not very directly related to the quake location, in order to give them media handles for discussion and easy identity.

Sections of the Hayward fault are slipping in “seismic creep” that means you can see the gradual movement (about as fast as a fingernail grows) by breaks in walls, buildings, roads. Other parts of the fault, and most of the San Andreas, lock together, building up even more stress as the creeping parts move. The locked parts only move in a rupture, which is another term for an earthquake. Hayward’s old city hall was abandoned because the fault goes right through it. Now that fault is a couple blocks away.

There are various ways earthquakes are measured: Acceleration: which is compared to the acceleration of gravity. Sometimes an earthquake can be more than or even twice the force of gravity. The biggest quakes (by energy released) don’t necessarily produce more shaking movement; it depends on surface composition and all sorts of other factors. Saturated and soft soils shake more.

During a quake, we measure shaking, but some techniques are improving that may give the ability to measure displacement as it happens. Various things are measured: P waves (Pressure; Primary) are like a sound wave in rock. They are the fastest thing emitting from the rupture and arrive first as a result moving at the speed of 6km/second. They feel like the come from below. S waves (Shear; Secondary) are the side to side waves. Love waves (named after a person) come third, more slowly, and are like a tail wagging side to side. Rayleigh waves are most destructive and shake in elliptical motion up and back then down.

P & S waves are generated mostly by the fault itself. Love & Rayleigh are mostly lensing and interference patterns caused by “sloshing” within the bedrock and the soils, waves reflecting off the earth’s mantle, other rock formations, fault surfaces, etc. The bay doesn’t effect the waves’ movement because it’s shallow. If you actually see the ground move in waves that’s probably a big quake and a Rayleigh wave.

Shaking measurement can be a crowd-sourced thing, too. Modified Mercalli Intensity is calculated from “measurements” or qualitative descriptions of many observers reporting how much they felt or damage they saw. Anyone can report in and should report — even if you don’t feel a quake that you heard about — this helps keeps the data accurate. Accelerometers in laptops and other devices (which exist to protect hard drive when dropped) can be networked to be seismographic info sources — all you have to do is download a free small application.

Since the biggest and worst earthquake damage comes last, early warning systems analyze the relationship between the P wave and S wave then try to get things in order before the later waves. This can provide a minute or two warning, depending on the distance to the epicenter — the farther, the more warning. An early warning might allow enough time to turning off gas and machinery, for example. Early warning systems in place since 1986 in Mexico (due to huge Mex City 85 quake) and Japan since 2008. This kind of technology is available now, but currently not for the general public, due to budget shortages and the complexity of psychology of how to get people to react appropriately. Currently PG&E, Google, BART and some others have access to a beta version only.

Earthquakes are located by triangulation using three or more stations. The origin is complex, because multiple places on fault can rupture at once. It might take years of computer models and analysis to determine all the sources, interactions and effects.

Shaking is a direct measurement and is not logarithmic; magnitude is a calculation and is logarithmic. A magnitude 7 has 30 times the energy released in a magnitude 6. Intensity maps created by Mod. Mercalli system have a downfall: they depend on how many people in a region report and how the regions are defined. Historical reconstructions of past quakes can use this method to calculate approximate magnitude of long ago quakes from diaries and news reports. Richter scale is used sparingly, it was designed for the LA Basin specifically and sometimes used for the quick and dirty first approximation. The numbers can change later after humans take a careful look after the original machine analysis. How long an earthquake lasts is one of the main factors in determining total magnitude (energy) released.

An aftershock is another quake, if the aftershock is bigger, than the earlier quake is re-termed a “foreshock”. Aftershocks can help determine length of rupture and depth. If they are getting father apart in time, they are aftershocks. They may or may not get smaller, though.

We can also take measurements after quakes: the offset if the quake rips the surface. A fault may be single line deep down but at surface it splays and splits, so there can be lots of offset measurements. 1906 is the first time offsets were systematically measured and the book of the report is huge. Nowadays LIDAR (portmonteau of ‘light’ and ‘radar’) is done from helicopter lasers. This sends signals to measure things on the ground and change is measure by comparing measurements to old data. InSAR measures deformation from space satellites. GPS is used for ground deformation measurements. They can track locations of fixed points and see that they are really not so fixed. There are so many new sensors that the split itself can now be measured as it happens in some places.

Contrary to popular opinion, small quakes don’t release enough energy to help prevent big ones later. You’d have to have magnitude 4 quakes every few minutes to keep the big one from occurring later. Stresses present when a fault ruptures don’t disappear, they just go and “bother” other faults bringing them closer to failure. Along the ruptured fault, the stress is reduced. At ends and bends the fault  increased stress shoots out. This explains sequences of quakes. We also can’t release stress by bombs but we can measure fault locations by echoes from explosions or ambient vibrations such as traffic. To see what’s happening inside Parkside section of San Andreas, they dug 3km through it and are now getting lots of data from deep inside. It seems magnitude ones hit every 32 hours. Even though it seems like clockwork in some ways, the overall system and larger ruptures are impossibly hard to predict.

Pushing and pulling of the crust is always going to happen on our planet. Faults don’t move except by the end extending and they don’t go away ever, unless that piece of the crust is subducted. Once it’s there, it’s a weak place in the crust and it can break more easily than surrounding areas.

Seismometers have only existed since the 1880s. Layers of soil accumulation show different offsets, and break the old surface at different depths from which years can be calculated. On Hayward fault they’ve done trenching and seven or eight prehistoric quakes show up so they know an average of one big quake every 120 years. On the Red Sea, trenching shows thousands of years of non-frequent quakes with very little deposition due to desert conditions. We can find shaking by precariously balance rocks. How long has it been there without being knocked down? We can tell by sun exposure changes — how long since it eroded into it’s current balanced shape.

Anatolian fault: calculations show that the next part set to go off (if pattern continues) is right by Istanbul. The San Andreas part that is considered highest risk is furthest south in Palm Springs. San Gregorio is “decently high risk” but in water so it’s harder to tell what it’s doing.

Dynamic modeling: more efficient than waiting to see what behaviors a fault shows. Modeling lets you get at the physics of the observations, and allows picking the problem apart into smaller manageable chunks. They can compare the model to past measurements and tell what can we possibly can expect from possible future quakes. This kind of modeling was hard to do until strong recently with ever increasing computing power. Multi-cycle simulators over time use a stress and re-stress model.

All measurements come together to create rupture maps. UCERF maps (# 3 just out last week) includes all the models and measurements. UCERF4 will include current modeling.

Hazard maps are made from the UCERF map and includes the likelihood of a rupture based on the underlying geology.

Fracking only produces small “induced” quakes and only if it’s done in an area where other faults exist and can be triggered. Southern CA for example would be a bad place to do fracking. They won’t make a fault, but any old place might have some old faults — like Oklahoma. The cause of these fracking quakes isn’t the frack but the reinjection of the water into the ground.

Quake predictions are not possible. The debate now is not: can we predict quakes with what we know; it’s, ‘Will we ever be able to know?’ These are inherently chaotic systems and may be too hard to ever predict.


  • Most powerful quake measured: Chile 1960 was magnitude 9
  • 911 was about magnitude 3
  • Hiroshima was magnitude 6
  • A 50 megaton bomb would be magnitude 7
  • The space rock that killed the dinos was mag 13!

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Life at Lake Merritt

Constance Taylor on June 19th, 2014 show us that the estuary Lake Merritt — sitting in the middle of a now dense Oakland — was once much more. It’s muddy tidal flats used to extend to where three of Oakland’s theaters sit, the Paramount, the Grand Lake, and the old parkway. It’s tidal channel was huge. The edges of the estuary were thick with grasses, tule, pickle weed, willows, and oak. Salmon, grizzlies, and elk could be found there, ducks could blacken the sky. The Ohlone, hunted there.

In the 200+ years since the Spanish came, the lakes edges have been gradually swallowed up by our streets, the mud flats covered. The “lake” is still connected to the bay and is influenced by its tides, but the waters are now regulated by a flood control station, so the tidal flushing is much less than it once was. The inflows are still there, but rains and our water systems bring down everything we leave on the street, trash and more.

And yet, life still seems to thrive here. Part of this is due to the protection the lake received early on. Mayor Merritt in the 1860s had a house built nearby and (so the story goes) got fed up with hunters when a cow of his was shot. It was declared a wildlife refuge in 1870, the first of its kind (at least in the West), and became a model for protections placed on other parts of the country. Bird islands were constructed at various times to allow for nesting habitat, and the islands, and parts of the waters remain off limits to people and their boats. Recent renovations thanks to a ballot measure are working on the tidal channel, exposing more mud flats, and making the channel more channel like (most prominently reworking where water flows under streets).

A recent bioblitz species survey done by the volunteers turned up 236 species in 5.5 hours of looking. Cormorants nest there most prominently, but you can also find black crowned night herons, snowy egrets, great blue herons, brown & white pelicans, caspian terns, cooper’s hawks, red tailed hawks, hummingbirds, grebes, crows, ravens, canadian geese, and all manner of gulls, ducks, and song birds.  Some of these like pelicans, egrets, and night herons weren’t seen here 30 years ago — they’ve come back from the brink after DDT did in their numbers.

You might also find things like the white line sphinx moth, the hummingbird moth, pseudoscorpions, a species of sand hopper crustacean that only lives in a small stretch of sand in Lake Merritt and in Chile.

There’s raccoons, squirrels (brought in by homesick easterners), skunks, and feral cats. There has also been and an otter which showed up one day in 2013.

In the water (which at its deepest is 10′) holds smelt, herring, moon jellies, bat rays, and leopard sharks. Come at the right time and you’ll find brown pelicans patrolling the shores diving, or at other times white pelicans floating scooping wide swathes of water. You can watch cormorants, coots, and eared grebes swimming through the water chasing small fish with astonishing agility.

There are also our invertebrates like spaghetti worms, crabs, snails, zooplankton, tintinnids, and phytoplankton. Much of the plants around the lake have been cultivated and planted there, but in the water there grows widgeon grass (which periodically gets mowed), and pickleweed still appears around the lake (both planted and volunteered). The oak trees that are on the north side of the lake would have been there, though those too were cultivated — by the Ohlone. The Ohlone also made use of the California buckeye fruit  as a fish poison (interestingly it is also toxic to European honey bees).

There’s also plenty of fungus — death’s caps, honey mushrooms, jack o’lanterns, and lattice stinkhorns can be found in the wetter parts of the year.

There’s slime algae & diatoms, sea lettuce. Bacteria mostly harmless, but occasionally the birds are still affected by avian botulism causing limp ducks. There hasn’t been an outbreak since 1971 — perhaps because of improved tidal flushing that has been managed over the years since.

Archaea are also found in Lake Merritt once thought only to be found in extreme environments — they are also common in mudflats where there is low oxygen. They help produce the methane which is responsible for some of what you might smell near Lake Merritt.

With all these things – all these representatives of all our kingdoms of flora and fauna – Lake Merritt is a fun place to visit and look for things.

We hope that we can see even more improvements to the environment over the years — the estuary though is a popular destination for all sorts of activities. Keeping it nice and making it better is not just the responsibility of our government, but you and me. The Lake Merritt Institute (http://www.lakemerrittinstitute.org) has long been helping to make it a cleaner and better place, but there is always plenty of trash to pick up, and they have self cleaning stations around the lake. You can also explore the wild side of Oakland at the Rotary Nature Center and with Constance’s organization Wild Oakland (http://wildoakland.org).

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Creeks to Sewers

Joel Pomerantz and Greg Braswell came out to talk to us May 15th about creeks and sewers. One particular creek in fact, Precita Creek, and how this creek was developed to the sewers that are there today.

Joel walked us through the natural flow of this creek and early history. The name Precita comes from a Spanish word meaning dam or weir. Native Americans would use weirs which were funnels with a basket in the middle into which they would drive the fish. The creek flows down from under where Market Street is today (from the Mission Mountains according to early maps), down along the north side of Bernal Heights and through the gap between Bernal and Potrero into Islais Creek. The creek has left it’s traces in odd little bends in streets (Joel was hoping to have Burrito Justice join us, but alas!).

The creek ended in the wetlands that pushed up through this gap, and the water joined Islais creek. For early San Franciscans this swampy area ended up in the late 1800s a perfect dumping ground for fill, effluents from tanneries and soap factories, and their sewers. The word fetid probably does not do it justice.

The first master sewer plan was in 1875, and many more have since followed. Before that there was a lot of add hoc sewers that did not really go anywhere (This talk almost cured me of my nostalgia for seeing San Francisco back in the day!). The first houses in this area were built in the 1860s and some had wooden sewers bringing waste down the hill.

The 1875 Humphrey plan had to get the state legislature to redraw streets for the plan to go forward. And it wasn’t til 1881 that a sewer was complete under (now) Cesar Chavez. The brick arch of this sewer was 11.5′ wide and 8′ tall. It’s had work done it since, but it is in essence still in use today.

The sewers extended out into the Marsh becoming the bones in a sense of later fill. The earthquake and fire of 1906 provided a lot of that fill.

The city didn’t see its first treatment plants to around the ’30s. Plants in Golden Gate Park and Fort Point. The SW treatment plant wasn’t built until the 40s. The city treats both sewer and storm water in one system — and for good reason — the water that falls onto San Francisco takes with it a lot of nasty crap, which we wouldn’t want pouring back into the oceans.

One could sense that Greg could tell amazing stories about just about any piece of our sewer system. Whether its current state, or how it came to be the way it is today.


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Most of us know Yerba Buena Island (aka YBI), if we know it at all, is from tunnel we drive through to get from one end of the Bay Bridge to the other. We may have even gone to Treasure Island, but Yerba Buena is a bit of a forbidding mystery — it’s current owners do not encourage visitors. Ruth Gravanis joined us April 17th, 2014 to uncover some of that mystery.

Two thirds of the island is still mostly owned by the Navy — although not for long, the intent is for them to hand the island over to the city. The other third is owned by the Coast Guard whose station will remain after the Navy is done for good.  Soon this island, will be a proper part of the city, and connected to the easy bay by a pedestrian & bike bridge, with new development slated for both it and treasure island. There is much to know and discover about this place.

~10,000 years ago, it wasn’t an island at all, but a hill in the broad valley that was soon to be the bay. The story of who lived there before the Spanish is still uncertain, but the Island seems to have been used by two different people’s of differing statures and burial practices. The island was used as a fishing camp and a place for gathering acorns. An extensive archeological survey was done, but details have been kept private.

The first westerner to name the island was Juan de Ayala in 1775, who called it La Isla de los Alcatraces (Island of the Pelicans — there is some controversy as to whether he called it this, or the map was transcribed correctly). For whatever reason, it was an English Captain, Frederick Beechy, who called named Alcatraz Alcatraz. He named Yerba Buena after the herb that grew all over the island at the time (the plant no longer grows there naturally).

The name didn’t entirely stick, it has been referred to as Sea Bird Island, Wood Island, and Goat Island. When the island became an official part of San Francisco in 1850, Goat Island was the official name. Goats had been exiled to island after they wrought havoc on the mainland. It was the petition by the Native Daughters of the the Golden West that brought the name Yerba Buena back to the island.

The Island was quarried in the 1860s and the stone was used extensively in Oakland and San Francisco buildings. The Army had a base on the island in the 1860s-1880s as well, but nothing remains on the island of this period. However, two buildings were moved to Angel Island. A lighthouse was built in 1875. Many of the trees seen on the island today are a result of an Arbor Day in 1887 where schoolchildren were brought by ferry to plant trees… a project of Sutro, General Vallejo, and Joachin Miller.

The Army handed over their base to the Navy in 1898 and officers mansions began to be built. Admiral Nimtz was the one of the last Naval officers in residents.  Aside from the mansions, the bridge, and treasure island, all sorts of things got built: administrative buildings, a 1 room schoolhouse, a mine factory, a tower for tracking ship movements.1973 the Coast Guard took up their third of the island. The Navy ceased operations on the island in 1997.

But the cultural/historical side of the island is no the only thing — it has a rich natural history as well. A rare plant study commissioned by the Navy found significant remnants of the original habitats, oak woodlands, dune habitat, tide pools, riparian scrub. A rich mix of native plants, insects, fungus, marine mammals, and birds.

There are many threats to these pockets, invasives like ice plant, eucalyptus (thanks to the Arbor Day in 1887). Eucalyptus isn’t completely without merit, it does provide roosting sites for falcons, and potential for bats, but they need light and space around them to let other things in (here in the Bay Area, not in Australia, very little grows under eucalyptus except invasive ivies).

The next question of course, is when the bike path comes in, and when the Navy has handed over the Island, what comes next. It is likely to become more of a recreation destination, more people will be living on it, and on treasure island, and we have to make sure we do not love it to death. A habitat and sustainability plan is already part of the development agreement, but there are still many things that have yet to be decided — how and where the bike path comes in being a big one.

You can follow the ongoing project at http://sftreasureisland.org

To learn more about the natural side of the island, check out this video from ShengChun Li, and the Treasure Island Museum


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Life in a Cubic Foot

David Liittschwager’s idea of one cubic foot partly started with the idea of having a manageable sample size (the talk was given March 20th, 2014). It is not an uncommon practice to find a limit around observations. So looking at a one cubic foot volume for visible species collecting at different times to find representatives of one day’s time. The size also reflects a common collecting practice of using 5 gallon buckets for collecting, and it is a similar volume.

But in has not turned out to be very limiting. The “dirty secret” for David is that he’s never really finished cataloging within those limitations. The biodiversity that can be found is amazing if we take the time to look. Even a pile of leaf litter in new york city turned up 100 species.

The spots to which he went were chosen by the likes of E.O. Wilson for the biodiversity they know is present. And the most spectacular of these locations have been tropical reefs. He flipped through amazing photo after photo of creatures collected from this little space and carefully sorted out to be identified and photographed.

All those creatures aren’t there all the time of course, but things move and water flows over the reef and through the open skeleton of one cubic foot. Collecting at different times of day and night then going through the process of sorting and identifying and photographing. It took about a month to come up with a representative sample of 24 hours. 

David looked up with some chagrin at a leafy acquatic plant, and said they should have spent time looking through the leaves, they would have found a ton more.

More recently he was out just at the mouth of the San Francisco Bay 100 yards west of the GGB, 100 yards south of the north tower, seeing what pass through a cubic foot of water as the tide moved in out, pulling in with a 300 micron net: mites, water fleas, tons of cephalopods, algae, crab and fish larvae, skeleton shrimp. With an 80 micron net they pulled in the glistening forms of diatoms. On a back of the napkin calculation, in a normal 24 hour period of spring tide, nearly a quarter million linear feet of water would pass through that cube — and maybe  2.6 billion creatures would flow through that space. 

David’s work in these small spaces shows us a different magnitude of beauty and grandeur, life, diversity, and abundance at scale we would not expect. Another lesson in all that we do not know about the planet we inhabit.

Find out more about David Liittschwager’s work at liittschwager.com.

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Living with Mountain Lions

Zara McDonald, President of the Felidae Fund, came to speak with us on February 20th, 2014.

Launched in 2006, the Felidae Conservation Fund does critical field research and conservation with cutting edge technology, innovative K-12 programs, and community involvement. There are 36 felid species, and all are in decline. These species are a powerful indicator species as they are apex on the food chain. They are being killed or dying  by habitat fragmentation, road kill, rodenticide poisoning, loss of genetic diversity, loss of native prey, illegal hunting and trade. Felidae’s education and outreach programs are designed to increase understanding and awareness and thus enable the conservation of  entire ecosystems. The Bay Area Felidae group is BAPP.

There are 40 common names for the Puma/mountain lion. The historic range was from the Yukon to the tip of South America, from sea level to at least 17,000 feet. In 1970 less than 600 pumas were in California. By 1990 the population was 117.

Females weigh up to 150 lbs., males up to 260 lbs. Measuring head to tip of the tail, the tail makes up 40% of the cats length. An adult males needs about 6000 calories a day. A female gives birth after about 90 days and can reproduce when there are 2 years old. Their litter is from 2-4 and the kittens are densely spotted. These spots fade as they grow up. Females need a territory of about 50 square miles, males from 100-400 square miles. They live solitary lives. Life span is 6-13 years.

There are a number of factors that continue to whittle at the number of pumas in the state.

One is depredation, and according to state law, if a puma attacks a pet or livestock in California, the owner can acquire a depredation permit to have the puma killed. In recent years, the number of permits issued has increased to about 100 per year. This number is higher than the sport hunting quotas in the states that allow puma hunting.

In order to help reduce this number, one of BAPP’s goals is to provide better education for pet and livestock owners living at the interface between the developed and natural worlds. Something as simple as keeping pets in at night, or using proper fencing or guard dogs for livestock, can reduce or eliminate incidents such as these, which protects both human-owned and wild animals, reduces community tensions, and minimizes the conflict between humans and the natural world. Rare incidences, 3/year in CA, of pumas being killed when wandering into developed areas are generally orphaned young males who’s mothers were killed and the young male was never taught to avoid humans for their survival.

Another is road kill which leads to the deaths of about 60/year in California. California’s habitats continues to be fragmented by ever increasing number of roads. When pumas cross roads to reach the habitat on the other side, there is significant danger that they will be hit by a car. Given their size this is not only dangerous for the puma but also for the human occupants of the vehicle.

To address this issue, the BAPP team is evaluating puma tracking data from the field research to locate frequent crossing points, especially on Highway 17 which is an especially dangerous road for pumas. Caltrans is now taking a pro-active approach to retrofitting roads with wildlife underpasses, and they have requested the data from the project as it becomes available to help guide their road development activities.

According to the California Department of Fish and Game, almost nine out of every ten reported puma sightings are not actually pumas. They are dogs, coyotes, bobcats, raccoons, deer…. even large house cats.

Though the increase in human-puma conflict is real and needs to be addressed, it’s important to keep in perspective that rather than challenging humans over the loss of their territory, pumas are quietly adapting to the encroachment and destruction of their habitat by adjusting their patterns, and are successfully avoiding conflicts with humans far more than we realize.

For more information and to help please visit Felidaefund.org and bapp.org.

(Thanks to Phillip Gerrie for this month’s notes!)

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