Yerington Nevada is part of the Wassuck Range, along the east side of the Mason Valley, in the southern Desert Mountains, and the Yerington area is known as the Singatse Range. Rocks in the Singaste range are of the Middle Triassic or older volcanic sequence .
There are two types of Volcanic rock that can be found out here. They are Intrusive and Extrusive. Intrusive rock generally is not exposed at the earths service . Technically speaking, an intrusion is any formation of intrusive igneous rock; rock formed from magma that cools and solidifies within the crust of the planet. This type of rock can be eventually exposed as weathering occurs allowing it to lay open for view.
Intrusive Rock
Whereas the later: extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff.
- Pyroclastics - are clastic rocks composed mainly of volcanic materials. Where the volcanic material has been lifted and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic.
- Tuff- is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is compacted into a solid rock in a process called consolidation.
When this Volcanic rock is formed Vesicles can form. These may have a vesicular texture. This type of tecture texture is characterized by the rock being pitted with many cavities (vesicles) at its surface and inside. As magma rises to the surface the pressure on it decreases. When this happens the gasses dissolved in the magma come out of solution, forming gas bubbles inside it. When the magma finally reaches the surface as lava and cools, the rock solidifies around the gas bubbles and traps them inside, preserving them as holes filled with gas, called vesicles.
Vesicles showing in the rock.
I hope you enjoy this as well as all my ECs out here. Truly a remarkable area. Please show the Earth Science value of this cache as well your knowledge after your visit by sending me the answers to the following questions.
Please feel free to take pictures and post them. I would just ask that you are selective and not leave to many SPOILERS for follow on cachers.
1) What is the difference between Intrusive and Extrusive Volcanic Rock?
2) What type do you find here?
3) These examples are very unique. Describe what you see.
4) Choosing an example, What is the texture of the rock?
5) How do you think that texture was created?
6) Walk further out into the landscape. Do you see other examples of the type of Lave Rock?