Friday Headlines, February 26, 2016
THE LATEST IN THE GEOSCIENCES
And the victory goes to the sponge
The King’s earthquakes
Title for ‘Earth’s first animal’ likely goes to sea sponges
Here’s the thing: Sponges are animals.
Once you get past that, the rest is fine. What makes an animal an animal is if it is multicellular, these cells aren’t all the same and must work together for the organism to survive, and the whole organism has to ‘eat’ other things to survive. This is in contrast to plants which are multicellular with different kinds of cells, but are capable of making their own food through photosynthesis.
Sponges are animals. Very, very simple animals, but animals nevertheless. They don’t have brains, or really any organs at all, but they have a skeleton that supports specialized cells for circulating water and capturing food particles, and other amoeba-like cells that take to food and distribute it throughout the sponge.
Sponges are animals. Animals that you can put in a blender and expect to get a living animal back out.
By looking for specific chemical compounds characteristic of sponges found preserved in rocks, scientists were able to determine that the oldest animals were either sponges or a type of algae. By looking at the genomes of sponges and algae, they determined that sponges were the older of the two types of organisms.
And so, the sponges have it! The first animals were sponges!
Andrew Lawson, in 1895, first named the San Andreas Fault in California. It was later, in 1906, at the time of the Great San Francisco Earthquake, that Lawson and other geologists understood for the first time that motion on faults were the cause of earthquakes.
Lawson was known a rather outspoken Scotsman, and because of this, he acquired the moniker of “The King.”
In 1895, two of Lawson’s graduate students described a new metamorphic mineral and named it after their advisor. Lawsonite is a silicate mineral composed of isolated pairs of silica tetrahedra along with abundant calcium and aluminum. It is a common mineral found at convergent plate boundaries where subduction is occurring.
As it happens, the lawsonite chemical structure contains water. As lawsonite is drawn deeper during subduction, the water leaved the crystal matrix, resulting in a mineral that is prone to cracking.
This cracking is the likely source of intermediate depth earthquakes (down to about 200 km below the surface), which have been a mystery for years.
“The King” Andrew Lawson, who died in 1952, would be happy to know that he still is responsible for shaking things up in geology.