Types of Rocks
A Rock Through Rocks
By Aidan Shuda
There are three types of rocks, sedimentary, igneous, and metamorphic. They are all formed different ways causing them to look different
Igneous rocks are formed from the solidification of magma or lava. Magma is the lava that is inside the volcano, but when it erupts it is called lava. When inside the volcano the magma can cool very slowly causing large crystals to form and causing the rock to grow larger and form differently. If a volcano erupts, lava with spill out of the volcano. Depending on the speed of the lava (also depending on the type of volcano; fissure, shield, etc) the lava will cool quicker or slower when exposed to the air. Either way the lava still cool very quickly and cause the crystals to be very small, even microscopic! Also, since the lava cools so quickly air can get trapped inside the rock causing holes. Sometimes this can even cause huge towers of basalt. Some full of holes. They are very cool to see if you look in the right places, like the Devil's Towers. Several types of igneous rocks are obsidian, basalt, and andesite.
Sedimentary rocks were once crustaceans and other sediment and lifeforms that died and fell to the bottom of lakes or oceans. Over time more sediment fell on top. Which is why it is called sedimentary rock. From the heat and pressure the rocks were cemented together and formed different layers of rock. If you look at places like the Grand Canyon you can see these sedimentary layers called strata. Also, sedimentary rocks are very brittle and over time these rock layers can start to collapse. Hopefully that wont happen to any of our wonders of the world anytime soon!
Metamorphic rocks were once either igneous or sedimentary rocks that were pressed under the earth's crust and melted and reformed. The structure of the rocks is partially melted and reformed. This causes the structure to become mixed creating a new rock. The rock type varies on the amount of pressure applied to the rock. One of the more common types of metamorphic rock is marble.