Module 2 Pigpen's Play Pen: Lesson 2.1 Devils Tower
Rock that forms when a pocket of magma collects beneath earth's surface, forming a bulge, then cools is called __________.
A laccolith
A laccolith is?
A laccolith is an infusion or bubble of lava that never actually broke the surface. Instead, magma seeped into a raised place under ground, forming a raised bulge. Again, the magma ceased flowing, hardened, and, after all other softer rock surrounding it eroded, the remains of the laccolith are what we see today.
Facts about devils tower?
Devils Tower is igneous rock surrounded by sedimentary rock It is made of phonolite, a very hard igneous rock It has a hexagonal structure - each tower is a heptagon or hexagon. The Devil's Post Pile is a pile of these columns that have fallen from the main structure.
Differential erosion is?
Differential erosion is the idea that different materials do NOT erode at the same rate. This makes sense when we think about it. Harder materials (rocks) are not as susceptible to wind or water or human erosion as softer rocks are. Also, a rock's chemical makeup may make it more likely to be chemically weathered than other rocks.
Laccoliths form when lava slowly seeps out of the earth, filling a depression or small valley with igneous rock. True False
False
Which of these is/are true of Devils Tower? It may be a volcano plug It may be a laccolith It is in Wyoming It is composed mainly of phonolite It is made of sedimentary rock It was formed by a volcanic eruption Its columns are octagonal
It may be a volcano plug It may be a laccolith It is in Wyoming It is composed mainly of phonolite
Phonolite is?
Phonolite is a hard, rather unusual igneous rock. It is what makes up Devils Tower. On a hardness scale, phonolite is between granite and basalt. In Devils Tower, the phonolite is surrounded by soft sandstone and other sedimentary rocks that are very vulnerable to erosion. One theory is that Devils Tower formed because the sedimentary rocks surrounding it weathered and eroded much more quickly than its phonolite. Therefore the phonolite columns outlasted the sedimentary rock surrounding it.
How does the concept of differential erosion explain Devils Tower? What are the two theories about the formation of Devils Tower?
Think about it
What can the different layers of soil tell us?
Think about it
Devils Tower is composed of igneous rock in hexagonal columns. True False
True
Geologists agree that Devils Tower formed by differential erosion, but disagree on the origin of its cooled magma. True False
True
A laccolith is ______________.
a pocket of magma that raised the rock and earth above it before it cooled
When different materials erode at different rates we call it ___________.
differential erosion
Igneous rock ___________ than sedimentary rock.
erodes more slowly
What is a volcano plug?
volcano plug is the remains of an ancient active volcano. The volcano ceased all activity, leaving this plug surrounded by softer rock which eroded away until it was left alone.
