Basalt, Obsidian, & Squishing Cups!

First, a little better picture now that the rock samples have dried from yesterday. This is what iron pyrite looks like from the bottom of the ocean. My pictures yesterday just did not do it justice. They are beautiful!

Do you know the difference between basalt and obsidian? How are these materials made? Today, more rock samples were brought up. Researchers on board requested some basalt and obsidian samples. Basalt most commonly forms as an extrusive rock, such as a lava flow. Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when lava extruded from a volcano cools rapidly with minimal crystal growth.

Obsidian is commonly found within the margins of lava flows known as obsidian flows, where the chemical composition (high silica content) induces a high viscosity and polymerization degree of the lava. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth.

Obsidian is hard and brittle; it therefore fractures with very

sharp edges, which were used in the past in cutting and piercing tools, and it has been used experimentally as surgical scalpel blades.

Here the obsidian is the rock in the center. It often forms over top of basalt.

A beautiful piece of obsidian glass.

And finally, my marine science students cups that they decorated shortly before I left in march. They are squished pretty small after being down 2,500 meters under the sea!

Storms moved in shortly before dark and it rained for a good part of the evening. Hope it goes away quickly!

See you tomorrow.