The first month on Cat Ba Island – getting my bearings

My apologies for the long gap between posts, life has been a bit busy.

I recently began a new position in Vietnam, on Cat Ba Island to be specific.  My first impressions are that this is a damp and precipitous landscape.  I have not seen the sun since I arrived in Vietnam on March 4th.  For Cat Ba Island this means a riotous profusion of greenery tempered by the steep terrain and lack of soil.

Where the northern end of the road terminates

Where the northern end of the road terminates

This is a land where Ymir’s bones lie close to the surface, broken and weathered, their calcium leaking back into the waters from which these precipitous cliffs rise.  The geology is the first thing that strikes you here.  The cliffs have been weathered by millions of years of rain, the ever-so-slightly acid rainwater eating into the ancient limestone creating a mature karst landscape.  Like bones, coral, and seashells, limestone is primarily made up of calcium carbonate, which in other forms makes marble and dolomite.  This is probably one of the reasons this is a place where snail diversity is immense, ranging from tiny frilled creatures more akin to limpets to giant land snails, many of which are still unknown to science.  Snails need lots of calcium to make their shells.

Unknown frill terrestrial snail

Unknown frilly terrestrial snail

Land snail shells collected around the office - and a wasp nest

Land snail shells collected around the office – and a wasp nest

The banded limestone found here is a relic of abundant diatom (a type of plankton) skeletons laid down five hundred million yeas ago and subjected to the vagaries of time.  Limestone, while soft to the chisel and hammer, is a remarkably durable stone at the macro-scale, one of the reasons climbers like it, but at a chemical level it is easily weathered.  We are often told that water has a pH of 7, that is it neutral.  Natural rainwater, we then assume, should also have a pH of 7, but it is closer to 5.6 due to the dissolution of carbon dioxide into the water making carbonic acid.  A pH of 5.6 is about as acidic as a cucumber or an onion for comparison.  Of course, other environmental factors can reduce this tremendously, leading to extremely acidic rain.  Rain falling on the limestone erodes small channels in the rock that look like thumbprints in wet clay.

Rainwater erosion on limestone

Rainwater erosion on limestone

Eventually these concentrate water flow, carving small holes in the stone reducing it to a swiss-cheese like structure with an extremely jagged and sharp exposed surface.  These little caves connect into larger caves.  In these protected, damp environments bacteria grow, exuding waste products and creating hydrogen sulfide that mixes with the water and makes a weak sulfuric acid, increasing the chemical weathering.  This cycle persists, eventually leading to enormous caves.

The airflow in these caves evaporates the mineral rich water tricking through the now porous stone and the calcium carbonate re-solidifies into stalagmites, stalactites, soda straws, and any number of strangely beautiful and complex cave structures.

Caves often form in weak portions of the stone and, eventually, gravity takes its toll and the weakened rocks collapse leaving behind steep spires and fields of slowly eroding boulders.

Limestone spi

Limestone spire in the north end of Cat Ba Island

Cat Ba and Ha Long Bay are examples of a drowned karst landscape, a mature karst landscape that has been flooded by rising waters.  What little soil does form is washed down into the many bays, coves, and channels of the region, leaving little for plants to sink roots into.  In the shallow waters of the bays mangroves find nutrients, in abundance.  Here mangroves are near the northern margin of their range, their numbers restricted and the trees short, making low dense forests.

Gray mangroves on the south western side of the island

Gray mangroves (Avicennia marina) on the south western side of the island

As in many places, the mangroves are in trouble here, often cut down to make shrimp farms.  This leads to reduction in local fisheries, increased erosion, and lack of protection from storm surges and tsunamis.  The local government is taking steps to protect what remains and to, potentially, restore some of the previous mangrove forests.  In the rich mud of the mangrove regions there are numerous animals, among them one of my favorites, mudskippers, amphibious fish that hop about in the mud protecting their little territories.

Mudskipper amongst mangrove roots

Mudskipper amongst mangrove roots

On the cliffs however there are few nutrients and plants grow in what cracks and declivities they can find.  As per many islands there are a number of endemic species, here one of the most commonly seen ones is the Ha Long Cycad (Cycas tropophylla), an ancient type of gymnosperm that looks like a cross between a fern and a palm tree.

Ha Long Cycad (Cycas tropophylla), endemic to a 400km square area, globally rare, locally abundant

Ha Long Cycad (Cycas tropophylla), endemic to a 400 square km area, globally rare, locally abundant

The season here is shifting into spring and some of the trees have begun blooming, among them the hoa gạo or Cotton Tree (Bombax ceiba), so named for the kapok-like fibers that are found in the seed pod.

Hoa Gạo (Bombax ceiba), Cotton Tree in English.  The Vietnamese name translates to "Rice Flower"

Hoa Gạo (Bombax ceiba), Cotton Tree in English. The Vietnamese name translates to “Rice Flower”

 

I still have not seen the little primates I came here to work with, they are few in number and they clamber about on the vertical cliffs like, well, monkeys.

Soon though.

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Chert – the birthstone of our species

Few types of stone have as long lasting and intimate relationship with our species as do those of the chert family.  Humans have been using this hard, glassy stone continuously to make tools since the time of Homo habilis, some 1.5-2 million years ago.  Our neolithic ancestors mined chert using fire to crack the stone (see video to see how it was done), at least 33,000 years ago at the Nazlet Khater site in Egypt chert was extracted from subterranean mines,  and flint (a type of chert) was used before we had matches to make fire, today we use crushed chert as the abrasive on some sandpapers, and to extract exquisitely detailed micro-fossils from the distant past.  When I worked as an archaeologist near Santa Barbara most of the projectile points, stone awls, and cutting tools we found were made from chert.

What is this “chert” we have been using so assiduously for the last 2 million years?

Chert is a microcrystalline stone made of silicon dioxide (SiO2) with a cryptocrystalline structure (crystals so fine that they are difficult to see even under a microscope) that lacks cleavage planes.  One of the most useful, for us, aspects of cryptocrystalline materials such as chert is that when they are struck they shatter in a predictable conical manner (conchoidal fracturing).  Obsidian and plate glass share this characteristic, making them and chert excellent for making extremely sharp stone tools.  Chert is more common than obsidian, but still rare enough that it was traded over great distances.  Another beneficial aspect of chert is that it is extremely hard, raking a 7 on the Mohs scale.

A number of well known minerals fall into the chert category: flint, jasper, radiolarite, chalcedony, agate,  and onyx are all types of chert, each with specific characteristics that give them enough difference from each other to warrant specific names.  The famous (and expensive) sharpening stones from Arkansas are made from novaculite, a porous, metamorphosed chert that makes an excellent abrasive.  Flints tend to be high quality cherts that are found specifically in chalk or limestone; these are deposited diagenically (via silicon replacement).  Chalcedony, agate, and onyx are a nested subset of minerals with chalcedony, a fibrous form of chert, being the parent of the group.  Jasper is usually found in association with volcanic activity and is sometimes considered to be under the chalcedony subset.  Jasper, agate, and onyx are popular semi-precious stones used for jewelry and sometimes intricately carved.

Red jasper cameo of Medusa by Benedetto Pistrucci (source)

What got me started thinking about cherts once more was a short day-hike I took with a friend in the Marin Headlands, those steep sided hills to the north of San Francisco that are so often obscured by the thick maritime fog.

Marin Headlands and the Golden Gate bridge partially hidden by fog

Marin Headlands and the Golden Gate bridge partially hidden by fog

The Northern California coast has a complex geology and is undergoing a number of divergent changes simultaneously.  This is an emergent shoreline (Geology of Northern California chapter 10, page 37), a place where the land is slowly rising in elevation.  Rising lands often suffer from high rates of erosion and the California coast has an even more drastic set of factors contributing to the erosion rare than merely rising land.  The bedrock is fractured by many faults, weakening the stone, earthquakes (most extremely minor) shake rubble loose periodically, and both wind and water eat away at the ocean facing slopes.  In addition, the sea level has risen several hundred feet since the last glaciation twelve thousand years ago, and the surf is greedily pounding on the hills, tearing parts of them away.

If you watched the video you probably noticed that the chert they were mining peeled off in plates, indeed that the whole formation was made up of sheets of stone layered atop each other like pastry dough.  About 50% of rock in the Marin Headlands is chert and has a similar texture.

Radiolarin ribbon chert cliff showing soft folds and a sharp fault-line cut

Radiolarite chert cliff showing soft folds and a sharp fault-line cut

This is ribbon chert, more formally known as radiolarite chert.  It gets the latter name because it is a biogenic stone made from the semi-gelled skeletons of radiolaria, a type of plankton that builds a silica based support structure.  These this rock was laid down over a 100 million year span beginning 200 million years ago and is filled with tiny fossils of the radiolaria.  Supposedly some of these are large enough to see with a standard hand-lens.

The folding tells us something interesting.  The folds in the above photo are smooth, meaning that this probably slumped slowly while it was still ductile.  Portions of the cliff have sharp folds where the rock broke, indicating that those deformations most likely happened more rapidly and after the stone had lost much of its ductility.

Red and greenish/blue indicate iron, either in oxodised or reduced form

Red and greenish/blue indicate iron, either in oxidised or reduced form

Much of the chert here is red, but there are many patches of vibrant blue-green and aqua as well.  The colors in chert indicate trace amounts of other minerals.  The red and the lovely greenish-blue are both indicators of iron, the red indicating that the iron has oxidised, the blue-green that it has been reduced (had the oxygen removed from it).  This is similar to the mottled gleying that one sees in wetland clay soils.  I am particularly fond of the blue and green colors in chert, perhaps because they are a bit more rare than the red.

Close-up of blue/green chert bands

Close-up of blue/green chert bands

The hardness of the chert leads to beaches with an interesting texture of sand, more like tiny glossy pebbles than the standard sand.

Chert sand

Chert sand

The combination of colors on the cliffs, beach, sky, and ocean make for a nice combination as well.

Tennessee Valley beach in the Marin Headlands

Tennessee Valley beach in the Marin Headlands

We have been using chert for nearly as long as we have been using tools, close to 2 million years now with no sign of slowing down.  If our species had a birthstone it would probably be chert.

A Long Flight over the Canadian Shield

Recently I flew from Istanbul to Los Angeles, following a great-circle route over Ukraine, Norway, Greenland, and Northern Canada.  As I always do when flying, I got a window seat and spent most of the flight peering out the window, developing a crick in my neck that took several days to loosen.

Much of the European and Greenland portions of the flight were shrouded in clouds, leaving me watching a vast expanse of what looked like glowing cotton.  Occasionally patches would open in the clouds and I would catch a brief glimpse of the land or sea below, and a look at one of the most talked about ecosystems on our planet.

Ice floes on the Arctic Ocean

Ice floes on the Arctic Ocean

The northern polar region, the Arctic.  This is a vast region centered on the bath-tub-like basin of the Arctic Ocean.  Discussing directions in the polar regions is tricky, for in the arctic, pretty much every direction that is not north is south, thus geography is a better indication of location than compass points.  On one side the entryway to the Arctic Ocean is narrow, shallow, and flows over the ancient land-bridge that once connected North America and Asia.  On the other side warm water flows up the Atlantic Ocean to the east of Greenland, keeping Europe warm and pushing the ice away from the Norwegian coast.  This is the primary point of water-flow into the Arctic Ocean.

To the west of Greenland a network of channels in the Queen Elizabeth Islands lets water slowly filter out of the basin, trickling back into the Atlantic via the southern opening of Baffin Bay.  Amongst the islands fierce currents keep polynyas open in the ice, providing open water for eider ducks and other sea-birds that over-winter in the Arctic.  Generally the whales will leave the Arctic during winter, but sometimes they become trapped and these polynyas provide the only places they can find air to breath.

Since we have been keeping records the sea ice extent has been getting smaller and smaller.  Records of sea ice extent and other cold-weather data can be found free of charge at the National Snow and Ice Data Center.

Several years ago, as part of a graduate project on Ringed Seals I looked at the changes in ice extent for the month of April over the last 30 years.  The photo of the broken sea ice above was taken on the eastern side of Greenland, a place where the sea-ice is extremely variable.

1981 - 2010 April Sea Ice Extent:  Darker colors indicate a greater number of years of coverage, lighter colors, fewer years of coverage

1981 – 2010 April Sea Ice Extent: Darker colors indicate a greater number of years of coverage, lighter colors, fewer years of coverage – green indicates areas outside of ice-cover that are shallow enough to provide foraging areas for Ringed Seals

The little flashes of ice I got to see through the grubby Turkish Airlines plane window were tantalizing, but they were only teases.  The interesting views were to come later, as we passed over the Canadian Shield.

Flying over over the Melville Peninsula, looking east to Foxe Basin... I think

Flying over over the Melville Peninsula, looking east to Foxe Basin… I think

Here, over the Canadian Shield, a 3 million square mile (8 million square kilometer) expanse of heavily weathered, exposed bedrock billions of years old the signs of past glaciation are evident.  Not merely evident, the fossil tracks of vast continental glaciers shout their presence to the sky.  Fortunately, I happened to be in the sky, with a camera at the ready.

There is a common misconception about glaciers.  People have heard that glaciers carve channels into the bedrock and grind down mountains.  This is only partially true.  Ice is not very hard, by itself ice can carve channels into rock the hardness of chalk or talc, but not into tough rocks like granite, the rock much of the Canadian Shield is composed of.  Ice levers out whole boulders and picks up loose material where it lies.  These become embedded in the ice and these are what does the scouring and carving.  The ice provides the weight and movement, much like a person provides the force when sanding or filing a piece of wood or metal, but it is the sandpaper or the file that does the actual cutting.

Ice, when it comes in glacier quantities, is an elasto-plastic material.  The upper surfaces are brittle and crack, making crevasses and seracs, but the deeper ice, down below the 50 meter mark, is more akin to a slow, cold silly-putty than to the brittle thing we put in lemonade.  When the ice is kilometers deep it oozes, flowing like spilled molasses over the land, dragging with it the entrained materials, grinding down high points, smoothing jagged surfaces, and hollowing out U-shaped valleys, leaving behind a stream-lined surface replete with the marks of its passage.

Rocky Mountain Trench in the Canadian Rockies - a classic glacially carved valley

Rocky Mountain Trench in the Canadian Rockies – a classic glacially carved valley

In both photos above the U-shaped valleys are clear.  These valleys come in all sizes, some more impressive than others.  The Rocky Mountain Trench in British Columbia is one of the more impressive ones, as is the Gilkey Trench in South-East Alaska.

The Gilkey Trench, the speck in the foreground is a person and each of the ripples in the bottom is 10 meters high

The Gilkey Trench, the speck in the foreground is a person and each of the ripples in the bottom is 10 meters high

These valleys are often found in mountains, places where the glaciers ground out material between the peaks, but left the high places alone.

Billions of years ago the Canadian Shield used to be home to vast mountains, now they are all gone, only their roots remain.  Erosion from various sources and repeated glaciations have scoured the Canadian Shield over and over again, grinding even the great mountains into low mounds, leaving traces that are best seen from the air.

Exposed bedrock showing fault-lines and ancient mountain cores

Exposed bedrock showing fault-lines and ancient mountain cores

The long, straight lines are old fault lines, places where geologic stresses broke the rock and let it slide against itself.  Here the rock is already damaged and the glaciers excavated long channels that look like canals from the air.  The distorted oval in the lower middle of the photo is where a bubble of rock forced its way up in the distant past, creating a mountain or large hill.  Now it has been ground flat and shows up in the surface pattern, much like cut wood shows the pattern of knots and grain despite being smooth to the touch.

Over much of the Canadian Shield soils are shallow to non-existent.  Even south of the tree-line vast areas are sparsely vegetated for lack of soil.  Roads are difficult to make as the land is smooth only at large scale and it is riddled with lakes and rivers.

In the winter the smoothest parts of the Canadian Shield are the lakes themselves and they are where temporary roads are made.

A road on the frozen lakes to the north of Yellowknife

A road on the frozen lakes to the north of Yellowknife

The last major glaciation was relatively recent, only about 20,000 years ago and the land is still recovering from the effects.  The whole Canadian Shield is undergoing isostatic rebound; with the weight of the up to 3 miles (almost 5 kilometers) of ice coming off the Earth’s crust it is now rising, seeking a new equilibrium as it floats on the liquid rock mantle deep beneath the surface.  Rivers and lakes are draining, the courses sometimes shifting as the land rises, carving out new pathways.  Water, like the ice it came from, does not do the work of carving the rock, it is the sediment it carries, but the Canadian Shield is made of hard stuff and it takes time to carve new channels in this durable granite.

Meandering rivers in glacial sediment

Meandering rivers in glacial sediment

Further south, the land is still flat, but has been overlain by a layer of sediment, left behind as the glaciers retreated.  Here rivers carve into the land more easily, looping back and forth and pinching off sections of themselves.  These oxbow lakes and the irregular rocky ones to the north are home to untold numbers of mosquitoes and other insects with aquatic life-phases.  These insects, when they emerge, lure birds from as far away as the southern hemisphere, and the mosquitoes become the bane of any humans wandering in the vastness of northern Canada during the warm season.  These insects, both adult and larval provide feed for numerous fish, making this an excellent place for fishing.  The first time my family and I drove to Alaska much of our food was from fish we caught each evening after only a few minutes with a line in the water.

The glaciers that covered the Canadian Shield were continental in scale.  There are only a few places where vast sheets of ice like that remain, but many places (for now) where small alpine glaciers are present, and even more places where signs of past glaciation are common.

One of the most famous of the post-glacial relics is Half Dome in the Sierra Nevada mountains of California.

Half Dome

Half Dome

The last interesting views I had out the window of my plane were of Half Dome, or Tis-sa-ack in the local native language.  This sheer rock-face is a batholith, a granite upwelling often making the core of a mountain.  Despite its appearance, Half Dome was not split in half, it seems to have formed more or less in the shape it has now.  Glaciers have smoothed and rounded the upper surface and carved out the characteristic U-shaped valley below though.

Glaciers have had a far larger impact on the world than most people realize.  Humans reached Australia some 60,000 years ago, able to walk over-land all the way to where Bali is now, needing boats only for a short stretch from Bali to Lubok.  Fifteen thousand years ago people walked from Siberia to Alaska over a broad grassy plain when the sea level was some 300 feet (91 meters) lower than today as a result of the water locked up in the ice.

When Greenland and Antarctica melt (which they will eventually do with or without our presence, the only difference is when it happens) sea level will rise by some 200 feet (67 meters) above present day levels.  At the moment there is a lot of talk of halting climate change via geo-engineering projects.  This is talk that completely and painfully misses the point.

The climate is a dynamic system, one that experiences wide changes over long periods of time, with the changes sometimes happening rapidly.  Yes, we desperately need to stop messing with the climate by releasing fossil CO2, methane, CFCs, and all the other greenhouse gasses we pump into the atmosphere with such abandon.  We are pushing the natural changes hard, forcing them to be of greater magnitude and to happen faster than they would otherwise.  We need to stop this, but what we do not need to and should not do is compound our mistakes by dumping iron into the oceans, pumping sulfur into the upper atmosphere, or place orbiting mirrors in space to deflect sunlight in a misguided attempt to keep the climate the way it was during the early 1900s.

We are driven by our economic system to keep things in some idealized stasis based on the time when we built our current infrastructure.  We may want things to stay static, but the earth is dynamic and fluid.  In our short-sighted, profit driven efforts to “save” our political and economic systems we will destroy the very thing that those systems and our societies are based on.

Seeing the earth from new perspectives and thinking about what we see tells us about the world is important.  We are on a cusp, we are standing on the edge of our metaphorical Half Dome.  We can tumble off the steep edge with disastrous consequences, or we can ease our way back down the slightly less steep slope, and once more enjoy the rich valley floor below.

Segovia: sandstones and granite

I have always loved things made of stone, especially ancient constructions.  The stone-masonry I have done has only increased my respect for the strength, vision, and talent of past masons.

Vermont garden wall

Small garden wall of Panton Shale for a friend in Vermont

Most of my stone projects have been small in scale.  The largest project was a 180 foot long retaining wall standing between 2 and 6 feet high, using 30 or 40 tons of stone.  That seems large when you’re doing it by yourself, but that’s a tiny project, barely larger than the little garden wall in the photo above.

In Peru there were some truly astounding pieces of megalithic engineering, many of them little known like Lanche and Kuelap, others well known like Saqsaywaman.

Walls at Saqsaywaman.  For scale zoom into the center of the full-size image to see the person.

Walls at Saqsaywaman. For scale zoom into the center of the full-size image to see the person.

Two days ago I went to the small Spanish city of Segovia and got to see several astounding pieces of stone-based architecture.  The first of these is the ancient Roman aqueduct.

The aqueduct in Segovia

The aqueduct in Segovia

The aqueduct runs about 15 km from the mountains into Segovia, with a 683 meter long raised section running through town.  The tall double arch of granite blocks is impressive enough by modern standards, even more so when you consider that it was built in the 1st or 2nd century, that the granite had to be carried in from the mountains, and that it is a dry-laid structure (no morter holding the blocks together) that has been standing for 1800 or 1900 years.  Clearly, this is a place with few earthquakes.

Granite is a favorite building material for many people.  It is an igneous rock that bubbles up in volcanic flows and cools in place.  The size of the crystals in the rock give an estimation of how long it took for the rock to cool and how much water there was in the melt.  The colors tell of the mineral content.  This granite is pale, with moderately large crystals weathering out, leaving the exposed stone extremely rough to the touch.

Due to the way it forms granite has no preferential cleavage plane, meaning that, given the right tools, it is easy to shape into whatever form is needed.  It is a dense and strong rock as well, another reason it is often used as a foundational material.

The blocks of stone making up the aqueduct are large, not enormous, but large, hundreds of pounds each.  At its highest point the aqueduct is 29 meters tall (that’s about as tall as a 4 or 5 story building).  Nearly 2 thousand years ago those blocks had to be hoisted up and set in place.  Clues as to how the Romans did so are carved into the blocks.

Lifting divots on the granite blocks

Lifting divots on the granite blocks

Each block was lifted into place with a pair of metal pincers, like those people used to carry ice-blocks with.  Divots were carved into the stone to prevent the pincers from losing their grip.  Presumably the divots were carved at the balance point of the block as well, a calculation I would be very curious to know how was done.

Supposedly Segovia was a “small outpost” when the Romans ran things in the area, though the effort and cost of building the aqueduct makes me question that assessment.  Small outpost or no, very little happened in the area for a long while, then in the 1200s the town began to grow and with that growth came the buildings that Europe is so well known for.

Castles and Cathedrals.  Segovia has impressive examples of both, the castle being the inspiration for Walt Disney’s version of Sleeping Beauty, and the cathedral being on the of the last of built of the great Gothic cathedrals.

Segovia cathedral

Segovia cathedral

Construction of the cathedral began in the 1500s, but took more than a century to complete.  The massive building looms over the city, glowing golden in the sunlight.

The first thing that struck me was neither the size nor the the tremendous amount of fine detail.  It was the color.  A warm, yellow/orange, not the color one associates with Gothic architecture, or with goths in general.  The castle, cathedral, and much of the rest of Segovia is made from this stone, not from the granite the aqueduct is made from.

The town of Segovia rests upon an outcrop of calcareous sandstone (sandstone with the grains cemented together by calcium rather than silica) and the land around rises and falls, exposing the bedrock in numerous small cliffs.  Sandstone is a sedimentary rock, a class of rock at the opposite end of the formation spectrum as granites and other igneous rocks.

Sandstone tends to have horizontal cleavage planes, refection the initial depositional patterns, and is often soft and easy to carve.  The sandstone in Segovia seems made for carving and the cathedral  builders took full advantage of this.

Cathedral detail carved from sandstone

Cathedral detail carved from sandstone

Sandstone weathers and erodes easily, especially in the presence of water.  Segovia, despite being a dry region by my standards (about a half meter of rain per year) is considered a wet place in comparison with nearby areas.  As such the builders took pains to protect the soft sandstone, making their waterspout gargoyles of the more resistant granite.

Cathedral gargoyle rain-spout

Cathedral gargoyle rain-spout

Statues of sandstone have not weathered as well as those of granite.

A royal lion slowly weathering away

A royal lion slowly weathering away

The the level of fine detail in the cathedral architecture is reflected elsewhere in the town.  The older buildings and the castle are covered with patterned façades.  In the past these patterns seem to have indicated which family owned the building and in a few cases older patterns could be seen under the more recent ones.

Old wall pattern, the material looks and feels like reconstituted sandstone.

Old wall pattern, the material looks and feels like reconstituted sandstone.

The castle, the Alcázar de Segovia, has a more simple pattern, but each intersection is studded with fragments of volcanic rock.

Looking up the castle wall to the battlements.  the small black studs are fig sized pieces of vesicular volcanic rock brought in from far away.

Looking up the castle wall to the battlements. the small black studs are fig sized pieces of vesicular volcanic rock brought in from far away.

Like many European castles the one at Segovia has gone through a number of iterations; fort, castle, palace, prison, artillery college, and museum.  It still serves the latter two roles.

The castle commands a wonderful view of the countryside in all directions.  One of the most magnificent views is of the cathedral:

Segovia cathedral from atop the Alcázar de Segovia battlements

Segovia cathedral from atop the Alcázar de Segovia battlements

In the opposite direction an old Templar keep and the sandstone cliffs much of the stone was quarried from to make the city are visible.

Templar keep and sandstone cliffs above the river below the castle

Templar keep and sandstone cliffs above the river below the castle

This has been a less science based post than most, but the trip to Segovia was far too interesting to keep all to myself.

The castle, aqueduct, and cathedral are the largest of the attractions, but not the only ones by far.  The food is delicious, mockingbirds flit about the city, interesting small plants grow from the old walls and on the red tile roofs, and great architecture abounds.

Small church in Segovia

Small church in Segovia

The Frontenac Arch a Critical Linkage

(this is an article I wrote for the summer 2012 newsletter of A2A – Algonquin To Adirondacks Conservation Association – a bi-national conservation association I am an adviser for – I wanted to wait until it was included in the newsletter before posting it here as well)

Between the Algonquin and the St. Lawrence a finger of the Canadian Shield, called the Frontenac Arch, reaches down from the north.  The Canadian Shield is an ancient formation of rock, heavily weathered, marked with meteor craters, and bearing the polishing scars of the ebb and flow of glaciers miles deep. Soils are shallow on the Shield, in many places nonexistent.  Nutrients are hard to come by and wetlands abound.

Red-winged Blackbird (Agelaius phoeniceus)

The bedrock to the east and west of the Frontenac Arch is old seafloor with thicker soils that are rich in minerals and nutrients. Groundwater flows through breaks in the flat bedding planes and does not become trapped in pockets as easily as it does on the Canadian Shield.

When we look at a landscape we often look at the plants growing on the surface and leave our thoughts on the surface with them.  Plants grow where they do because of the chemistry of bedrock, soil, water, and temperature.

On the Frontenac Arch the chemistry of the northern and the southern Canadian forests mix.  This mix shows in the wide and unusual range of plants growing in and around the Frontenac Arch.  The diversity of plants attracts a corresponding diversity in animals. All these plant communities are separated and connected by the dense wetlands, and many animals are drawn to the wetlands.  Frogs, fish, ospreys, turtles, feeding moose, waterfowl of all sorts, beavers, blackbirds, otters, sparrows, loons, and many more.

Male Painted Turtle (Chrysemys picta)

Healthy wetlands are rich in species, both in number and diversity; plant, animal, insect, and bird.  Wetlands are the kidneys of the planet; they filter water and keep it clean.  They slowly recharge aquifers with cool, pure water, they keep rivers and streams clear, they trap sediment, and they eventually fill in, becoming rich, complex soils full of nutrients.

Oddly, perhaps counter intuitively, all this life, more specifically all this diversity, of living things in wetlands is what keeps the water clean.  The water is strained at a molecular level for nutrients by all those living organisms.  Each looks for different things and uses them differently.  Toxins and chemicals are swept up and broken down by this process, but only as long as the diversity of life is present.

When that fabric of diversity is broken the health of the land suffers.  A healthy environment is like good glass, so clear you don’t see it and tough enough to withstand storms.

A large male Snapping Turtle (Chelydra serpentina) and feral biologists

The Frontenac Arch is one of the gems of the region and is critical in connecting the northern and southern forests.

*          *     *     *          *

For those who are interested the Algonquin to Adirondacks Conservation Association website is here, and a map is below:

Algonquin to Adirondacks Conservation Association map of the Frontenac Arch

Away Dog! Apocynaceae, the Dogbane family

Near my house, next to the road the ground is sandy with a scattering of pebbles in the mix.  Like much of Vermont what is not bedrock is ground up glacial debris deposited when the vast continental glaciers melted away.  The ground is sandier than most places at my house because I am perched on the southern slope of a small rock outcrop, a place where the downward pressure of the glacier was lighter, water flowed under the ice, and fine sediment was deposited.

In that sandy ground there are wild strawberries, mosses, dandelions, fleabane, hay scented ferns, a few coneflowers, some potentillas, Allegheny blackberry, a little bracken fern, and a small stand of dogbane (Apocynum cannabinum) with delicate pink flowers.

Hemp Dogbane (Apocynum cannabinum)

Before moving to Vermont my only experience with this plant was via books.  I always wondered why it was called Dogbane.  Was it like negative catnip for dogs?  Or was it simply toxic to dogs?  Apparently it is a toxin, and not just to dogs.  Ingestion of any portion can induce cardiac arrest and both the family and genus name literally translate to, “Away Dog!”  Apocynum cannabinum has, thick, milky sap, much like a milkweed, indeed Milkweeds (Asclepiadoideae) are now considered to be a subfamily of the Dogbanes (Apocynaceae).  Other members of the Dogbane family include two of my least favorite plants, Oleander and Vinca, both from the Mediterranean and common in California where they were introduced as ornamentals.  Oleander can be seen in any urban environment in Southern California, most often as a highway divider plant.  The sap is extremely toxic, raising painful rashes, and the smoke can be lethal if inhaled.  Vinca, more commonly known as periwinkle, is  common in Northern California where it invades riparian areas, covering both ground and small trees in a dense, vining mat of glossy green leaves studded with pretty blue flowers.  It is nearly impossibly to eradicate once in place.

In the past some Apocynaceae species were used to make a poor quality rubber, others for toxin to apply to arrows.  Some species produce edible fruit and others edible flowers.  We extract heart drugs from a few of them as well.

The dogbane in my yard, Apocynum cannabinum, is a traditional North American source for extremely strong fiber, hence the “cannabinum ” species name, referring to the hemp-like characteristic of the plant.  Common names run from simply Dogbane, to Indian Hemp, Wild Cotton, and Hemp Dogbane.  The fibers are stripped from the stalk in late fall and can be twisted into a fine, strong cord.  Cords made from dogbane were prized for their great strength and used for sewing, fishing lines, and other work requiring fine cordage.

The Hemp Dogbane ranges from calf high to chest high.  The ones in my yard top out at waist high.  The have an odd branching structure, perhaps best described as irregular opposite.  The main stalk continually divides in a binary fashion, with one side acting as a dominate leader, this pattern is often repeated on the side branches, but in some cases buds on both side of the stem will form side branches instead.  The result is a roughly Y shaped plant that rapidly spreads as it grows.

Apocynum cannabinum whole plant.

The leaves are opposite and the undersides are covered with a fine pubescence.  I expect that the hairy leaves are an adaptation to help cope with moisture stress.  Plants often evolve this trait to create a boundary layer of trapped, still air that aids in preventing moisture from being blown away.  The upper leaf surfaces have a matte waxy texture, a little like nasturtium leaves.  Water beads and runs off of them rapidly.

Apocynum cannabinum leaf hairs

The seeds are held in long, horn-like pods.  This time of year few of the seed pods have developed, but a couple of plants are a little further along in the cycle than others.

Apocynum cannabinum seed pods, not fully developed

Few of the leaves have any insect damage, but the flowers are popular with a number of insect species.  I’ve seen ants, flies, bees, and moths going to them.  Hidden amongst the flowers are predators as well.  The Goldenrod Crab Spider (Misumena vatia) seems fond of my dogbane.

Goldenrod Crab Spider (Misumena vatia) playing parlor games with a fly

Goldenrod Crab Spiders are so called because they often hide amongst the bright yellow flowers of goldenrod, a common meadow plant in New England.  The spiders change color from white to yellow and back again based on input from their eyes.  The yellow color seeps up to stain their carapace, providing camouflage.  When they move to a pale flower the production of this pigment stops and the spiders slowly turn white once more.  Experiments show that the spider will not change color if it cannot see what color plant it is on.

These are not web building spiders, they are ambush hunters, grabbing unsuspecting prey in their wide arms.

The smell of the flowers is odd and difficult to describe, incorporating many scents including a dusty sweetness and a faint rankness like dried meat on the edge of going bad, but they are pretty.

The Mighty Dragonfly

Of all insects there are few that capture our attention and interest the way dragonflies do.  They have, perhaps, the coolest, most evocative name of any group of insects: Dragonfly.  In English there are a great number of other common categorical names: Devil’s Darning Needle, Snake Doctor, and Ear Cutter among others.  Many of these names come from the mystifying apparent fear of nature that crops up over and over in European views of the world.  Many European cultures viewed dragonflies as sinister creatures, servants of the devil, in league with other evils such as snakes and bats.

Other cultures, often more agrarian ones, had a far more benign view of dragonflies, based, perhaps, on the recognition of their fundamental role in controlling populations of pest insects of all sorts.  An archaic name for the Japanese Islands is Akitsushima (秋津島), the Dragonfly Islands, where dragonflies symbolized courage, strength, and happiness.  For some native American tribes dragonflies symbolized clean, pure water, swiftness, and agility.  In the modern world dragonflies are good indicators of environmental heath, indicating a robustly functioning ecosystem.

Libellula quadrimaculata – Four Spotted Skimmer
The Alaskan State Insect

Dragonflies and their close relatives, Damselflies, come in a dazzling array of colors and patterns, ranging in size from less than  an inch long up to the South American Megaloprepus caerulatus with a wingspan of over 7 inches.  The largest dragonfly we know of is from the 300 million year old fossil Meganeura that had a wingspan of over 2 feet.

Dragonflies are powerful hunters, both in their nymph and adult stages.  Dragonfly nymphs are aquatic and prey on any animal or insect they can grab with their claws or their extendible jaws.  Insects, small fish, tadpoles, and small amphibians are all food for these voracious predators.  The nymphs are large, and, in turn, are prey for a wide range of other animals, insects, birds, and fish.  Elva Paulson has some wonderful watercolors of a dragonfly emerging from its nymph stage.  Humans are included as predators, many Asian cultures eating both dragonfly nymphs and adult dragonflies as delicacies.  One of the most tasty things I’ve eaten (from a long list of foods most people would consider to be unusual) was a plate of deep fried dragonfly larvae.  Absolutely delicious.  In Beijing I would sometimes find adult dragonflies candied in liquid sugar, their wings crispy with the hardened sugar.

Unknown green dragonfly – note the barbs on the forelegs for catching prey

The adult phase of a dragonfly’s life is short, in temperate climates only the length of the summer.  This is their mating stage and it takes them between 2 months and 6 years living under water to reach this stage.  Dragonflies are extremely active during this mating phase and must eat often.  They have enormous eyes giving nearly 360 vision, incredibly swift reactions, fast, powerful flight, and wicked barbs on their legs to assist capturing insects in flight.  The inset above shows these barbs.

Libellula exusta – White Corporal (I think)
eating its prey

The common names of dragonflies often reflect their speed or their abilities as hunters.  Meadow-hawk is one of my favorite names, and watching one dart away to catch an insect and return to its roost to devour it definitely brings hawks to mind.

Libellula quadrimaculata – Four Spotted Skimmer
note the different wing heights

Dragonflies are powerful fliers.  They have been clocked at over 35 miles an hour, fast enough to get a speeding ticket in a school zone, and, like hummingbirds, can fly forwards, backwards, sideways, up and down, and hover.  Their backs are sloped where their wings anchor, placing each pair at different heights, allowing for tremendous wing mobility.  Some species of dragonfly migrate, but the scale of some of those migrations has only recently been realized.  One dragonfly species in particular, the Globe Skimmer (Pantala flavescens) flies from India to Africa and back, island hopping cross the Indian Ocean, making open water crossings of nearly 1000km (620 miles) between island stops.  The only places they can breed are at the Indian and African ends of the migration, many of the islands they use as stopover points do not have sufficient freshwater for dragonflies to breed.  This is a stunning feat of flying for an insect and may be a behavior that evolved as a result of plate tectonics splitting India and Africa apart, eventually thrusting India into Asia.  If so, this migration could have begun 135 millions years ago.  Unfortunately, we have no reliable way of telling if this is the case.

Last year was a good year for dragonflies in Vermont, and this year looks like it is shaping up to be a good one as well.  The ecologist in me cannot help wondering why and one idea is that it may be linked to the calamitous drop in bat populations as a result of white-nose disease, a fungus that infects hibernating bats, weakening and eventually killing them.  It may be that adult dragonflies have more to eat with fewer bats and a greater percentage of them are surviving through the summer.  There is a historical precedent for this sort of boom in insect populations.  During the Great Leap Forward, Chairman Mao promoted a policy of killing off all things he thought were eating grain, birds amongst these.  With the crash in bird populations in China the insect population exploded.

Unidentified dragonfly – maybe a Darner of some sort

I am happy to see the dragonflies here.  Their presence means that the water is clean, we will have fewer mosquitoes, midges, and black-flies, and they are extraordinarily beautiful creatures.

Three-hundred twenty-five millions years old and going strong.  They have it figured out!