Wednesday, April 28, 2010
D says: Finally! I get to learn about Geology (the study of rocks). Right now I am just classifying rock samples but it's still fun. The three types of rocks are igneous, sedimentary, and metamorphic. There is a rock cycle, similar to the water cycle. Hot molten rock flows from volcanoes, which cools and forms into igneous rocks. Then the igneous rocks form into either sedimentary rocks or metamorphic rocks. Sedimentary rocks form when layers of igneous rocks push down on each other, and the rock compresses and changes. Metamorphic rocks form when igneous or sedimentary rocks push down deep into the earth where it is hot. It's hot there but not hot enough to turn the rocks into magma yet. Instead they bake and change into metamorphic rock. Metamorphic and sedimentary rocks can turn back into magma and when the magma cools down they turn back into igneous rocks. And that's the rock cycle!
The definition of a rock is that it has to have two or more minerals that make it up. The definition of a mineral is that it can only have one type of molecule so it is only made up of one thing. Some common minerals are sufur, fluorite, mica, quartz, and hematite. My favorite mineral is sulfur and my favorite rock is obsidian, an igneous rock. The lightest rock is pumice, an igneous rock. It is so light that it floats. Coal is a sedimentary rock that is made up of the remains of bones and several other minerals. Basalt is the most common type of rock on the earth. It is an igneous rock. Another interesting fact about it is that the moon is mostly made of Basalt. My second favorite rock is a metamophic rock called dolomitic marble.
I like rocks!