Vesicular texture is a term for when a rock contains holes left by bubbles that popped when gas escaped during its formation. That’s right…bubble fossils! They are often found in rocks that come to the earth’s surface, such as basalt, which forms much of the rocks here in the Snake River canyon. The geology you see here exists because rhyolite (hot) and basalt (hotter) erupted from magma inside the earth, cooling off to create igneous rock formations. The rapid decrease in pressure caused bubbles to form and pop.
At the posted coordinates, you will see some rocks with unique vesicular texture. To log the EarthCache, answer the following questions in a message:
-Pick three bubbles and describe their shapes and sizes.
-Are the bubbles more clustered together, or spaced out? Describe what you see.
-Why do you think this particular rock face is here?
-Why do you think some of the bubbles are so large?
-Describe the color of the basalt which makes up the rocks here. If it’s darker-colored, it contains pyroxene minerals (often grayish or black). If it’s lighter-colored, it contains a lot of plagioclase (a whitish sort of crystallized mineral). Do you think the rocks here contain more pyroxene minerals, or plagioclase?
Sources: Visit Southern Idaho, Humboldt State University and University of Pittsburgh igneous geology guide websites, ScienceDaily