Two Trees from Socotra

Socotra, part of the Republic of Yemen, is a small archipelago of four islands in the Arabian Sea off the Horn of Africa. Socotra’s isolation from the mainland combined with a tropical desert to semi-desert climate has lead to unique speciation, with more than a third of its plant life being found nowhere else on Earth. The islands contains a wide range of habitats: beaches, mountain ranges, plains and caves. Because of Socotra’s broad diversity it has been described as the strangest-looking place on Earth. 

The dragon blood tree (above) and the cucumber tree (below).

   One of the most impressive of Socotra’s plants is the dragon blood tree (Dracaena cinnabari), which looks very odd with an umbrella shape. Its red sap was thought to be the dragon’s blood of the ancients, sought after as a medicine and a dye since antiquity and highly prized by European Renaissance painters. It was also used as a varnish by 18th century Italian violin makers. 
   The unusual shape of the dragon blood tree is an adaptation for survival in the dry rocky soil where it is found. The large, packed crown furnishes shade and reduces evaporation which helps seedlings survive beneath the adult tree.
   Perhaps the strangest of all the trees on Socotra is the cucumber tree (Dendrosicyos socotranus), which looks like a giant cucumber with its bulbous trunk and tiny crown. It lives on the dry parts of the islands up to about 500 meters in elevation. It is the only tree in its plant family which includes melons, gourds, squashes, and yes, cucumbers.
   Cucumber tree seedlings are eaten by goats that graze on the islands. Mature trees are often cut down and made into pulp which is fed to livestock. The leaves of the cucumber tree are used by the local population to treat a variety of ailments.
   Socotra’s ecosystem is one of the most endangered in the world and it is listed as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). Both the dragon blood tree and the cucumber tree are considered vulnerable species by the International Union for Conservation of Nature (IUCN). 

Fly Geyser

Fly Geyser is a small, 1.5 m high geothermal geyser that is located near the edge of Fly Reservoir, Nevada. The Geyser was accidentally created in 1916 during the drilling of a well when a shaft was drilled in hopes of striking water to turn part of the surrounding desert area into farmland. The well functioned normally for several decades, but then in the 1960s geothermally heated water found a weak spot in the wall and began escaping to the surface, turning the area into a desert wetland. Dissolved minerals started rising and piling up, creating the mount on which the geyser now sits. 

Today, water is constantly squirting out reaching 1.5 m in the air. The geyser contains several terraces discharging water into 30 to 40 pools over an area of 74 acres. The geyser is made up of a series of different minerals, which gives it its beautiful colors. Recently, yet another new geyser has formed. For unknown reasons, the original geyser has gone dormant. One hypothesis explaining this is that later geysers robbed the original of its water supply.

Fly Geyser is a secret tourist attraction located about 200 km north of Reno, Nevada. The Geyser is located in Hualapai Flat, about 0.5 km from State Route 34. It is large enough to be seen from the road. Fly Geyser is located on the privately-owned Fly Ranch and is accessible only by a small dirt road. 

No quiz this week due to summer vacation!

Planetary Moons

Did you know that over 170 natural satellites orbit six of the eight planets in our solar system? Take the quiz below to see how much you know about this diverse group of celestial bodies.

The seven largest moons of the solar system, with Earth for scale.

Killer Lake

Perched on the flank of an inactive volcano in northwestern Cameroon lies a lake with a dark past. One of only three of its kind on the planet. Its name is Lake Nyos and it contains high levels of carbon dioxide. But this lake is not famous for harmless bubbling mineral water springs. This lake is a killer.

Lake Nyos shortly after the eruption. On the right you can see the aftermath
of a large wave that scoured the shore and knocked down trees.

   Lake Nyos sits in the crater of a dormant volcano. 80 kilometers beneath the lake is a pool of hot magma that continually releases carbon dioxide and other gases. These gases travel upward through the earth's crust and get trapped in natural spring water which feeds into the lake.
   This by itself should not be particularly hazardous, and normally the carbon dioxide would escape harmlessly into the atmosphere. But Lake Nyos is fairly deep, and in the tropics. So the CO₂ collects in the cold water at the bottom of the lake. Tropical lakes are typically still and there is not a lot of mixing of their water layers, and Lake Nyos is no exception. Also, the water at the bottom of this lake is cold and under great pressure—ideal conditions for dissolving large quantities of carbon dioxide. The result of this perfect storm is that over time the bottom of the lake becomes saturated with gas. This creates a dangerous situation where the CO₂ can spontaneously erupt if there is a disturbance such as a landslide or small earthquake. 
   And while the eruption itself isn't a problem, the suddenly release of carbon dioxide can be very dangerous. CO₂ normally makes up only a very small percentage of the atmosphere, only 0.03%, and concentrations of 10% or more can cause suffocation. 
   This all played out on August 21, 1986, when a cloud of carbon dioxide gas suddenly belched out from the lake. Since CO₂ is 1.5 times heavier than air, it poured over the rim of the crater and rolled down into the surrounding valley. It's estimated that the lake released 1.6 million tons of carbon dioxide in a cloud 50 meters tall that rushed down the valley for about 23 km, suffocating nearly every living thing in its path. 1,700 villagers and 3,500 livestock living around Lake Nyos were asphyxiated by the deadly cloud.

The pipe that was installed to to pump carbon dioxide
from the bottom of Lake Nyos.

   In 2001, an international team of scientists, with funding from the U.S. Office of Foreign Disaster Assistance, installed a degassing pipe in the lake in an effort to avoid another disaster. The pipe allows water to be pumped from the bottom of the lake, creating a fountain to release the carbon dioxide harmlessly into the atmosphere. However, more pipes are needed, and the area has since then been repopulated. It may only be a matter of time before this lake strikes again.

Putting the Pop in Soda

What a better way to beat the heat this summer than by enjoying a nice cold soft drink. It’s also a great excuse to learn a little chemistry! We all know that carbon dioxide is what puts the fizz in soda pop, but why not some other gas, say nitrogen for example?
   First a bit of history. In 1767, Joseph Priestley discovered a method of making carbonated water by hanging a bowl of distilled water above a beer vat at a local brewery. Priestley found that water treated this way had a pleasing taste, and he offered it to friends as a refreshing beverage. 
   In 1772, Priestley published a paper that described dripping sulfuric acid onto chalk to create carbon dioxide gas, then dissolving it into a bowl of agitated water. This process would be improved upon by others and eventually sold to pharmacies for commercial use. Before long, pharmacies were adding flavors to their soda water and the soft drink was born.
   Now back to our original question. Why carbon dioxide instead or nitrogen or oxygen? Carbon dioxide is used in fizzy drinks because it’s more soluble in water than nitrogen or other potentially suitable gases. At room temperature, you can dissolve about 1.75g of carbon dioxide into a liter of water, compared to about 0.02g of nitrogen per liter of water, and about 0.04g of oxygen in one liter of water. So, out of the readily available, nonpoisonous gasses in our atmosphere, carbon dioxide is by far the most soluble.
   Carbon dioxide dissolved in water at a 0.2–1.0% concentration and creates carbonic acid. This gives the water a slightly sour taste with a weakly-acidic pH of about 3.7 at normal bottling pressure. An alkaline salt, such as sodium bicarbonate, may be added to reduce the acidity and mimic the taste of natural spring water. This is how carbonated water came to be known as soda water, and is also the difference between seltzer water and club soda—the former does not have any sodium bicarbonate added to it.

Stromatolites

A cross section of a stromatolite showing
its characteristic dome layering.

The Pilbara region of western Australia is home to some of the Earth’s oldest rock formations, and among these formations are remnants of an ancient reef. This is no ordinary reef made of coral; it’s made of stromatolites—structures left behind by microorganisms that lived 3.5 billion years ago.
   Stromatolites are formed by algae that live on the floors of shallow seas. They collect fine layers of sediment that are built up into cones, domes and other shapes over many millions of years. A stromatolite is not alive, but is a structure made by living things. When we find one in the fossil record, it's like finding an ancient footprint. 
   The microbes that make these structures are almost never preserved as fossils inside the stromatolites. And without that it's difficult to be sure an ancient stromatolite is proof of life. But the Pilbara stromatolites are not only biologically produced, but possibly the oldest evidence of life on our planet. 
   These amazing structures have a pronounced conical shape unlike any kind of ripple pattern you would expect to see on a lifeless sea floor. Instead, stromatolites are sedimentary structures formed usually by cyanobacteria (also known as blue-green algae) that live in the interface between sediment and ocean. By examining these structures, we can tell that some lived almost 3.5 billion years ago, forming near rocky coastlines with shallow water environments. They have not been found in deep water areas that were also in existence at that time. 

Stromatolites at Shark’s Bay are fossil ancestors
to the oldest known life form on Earth.

   These fossilized ecosystems provide a glimpse of the Earth’s early history and possibly the beginning of life on our planet, as they are thought to be largely responsible for oxygenating Earth’s early atmosphere. Could life have existed even earlier? It’s possible. We don’t have any geologic record of the first 500 million years of Earth’s existence, so there is a pretty big gap in our knowledge. What's not preserved in the fossil record is how life formed in the first place. One thing we do know: that stromatolites are very distinctive and these structures are nearly identical with those of living stromatolites found at Shark's Bay, in western Australia. That means these living fossils have a family tree that stretches back farther than any other living thing on the planet. Remarkable, when you think about it.

Dragons of the Cretaceous

A giant azhdarchid compared to a giraffe.
Illustration by Mark Witton/University of Portsmouth.

Pterosaurs are flying reptiles that lived between about 230 and 65 million years ago. Although often called dinosaurs, they are actually a distinct branch of reptiles that independently evolved flight. There have been about 100 species of pterosaurs discovered so far, and one group of about a dozen species—the azhdarchids—is of particular interest. 
   In 1971, a student from the University of Texas working at Big Bend National Park discovered a long, hollow fossil bone that was from an enormous azhdarchid wing. Excavations recovered more wing bones, but no body bones could be found. It was named Quetzalcoatlus northropi, after the feathered snake god worshipped by the Aztecs. Eventually, other specimens of Quetzalcoatlus were found at the park. These specimens were smaller but more complete than the original, and by comparing them with the massive bones of the original, they were able to calculate the body size of the original specimen. This creature had an estimated wingspan of 10 meters or more and a height of over 5 meters. With a massive, elongate head, long, stiff neck and long hind limbs, this was a real-life dragon (minus the fire-breathing of course!) and the largest flying creature to have ever been found.
   Despite their huge size, azhdarchids were able to quickly launch themselves into flight from level ground by leaping from all four limbs from a standstill, without the need of cliffs. Azhdarchids were most-likely flap-gliders—capable of short bursts of powered flight while covering long distances by soaring on thermal currents.

A group of Quetzalcoatlus northropi, foraging
on a Cretaceous fern prairie. Illustration by
Mark Witton/University of Portsmouth.

   Azhdarchids have often been portrayed as feeding by grabbing fish as they skimmed the water, but it is more likely that they stalked their prey on land. Their fossils are usually found with terrestrial dinosaurs more typically found in semi-arid inland plains. They were well suited for walking and had feet that were small and padded, better for walking on solid ground rather than wading. They preyed on small dinosaurs and other animals up to the size of a large dog. Like a modern-day stork, an azhdarchid would pick up its prey, toss it to the back of its mouth, and swallow it whole.