When most people look at rocks they see….well, rocks. Lumps of soil and hard chunks of earth of different shapes and sizes. Maybe you collect them, or climb them, or use them in your garden. But geologists know the hidden truth about rocks – they help tell the earth’s history!
There are 3 types of rocks: Igneous, Sedimentary, and Metamorphic. Rocks can change from one type to another through different processes like melting or pressure.
Igneous rocks are usually associated with volcanoes. They are formed deep in the Earth’s surface by the cooling and solidification of molten magma or lava. Examples: basalt, pumice, granite
Sedimentary rocks can take thousands of years to form. Layers of gravel, silt, sand, and even dead plants and animals are slowly deposited on top of each other. As layer after layer pile up, the bottom layers are pushed down and become tightly compacted together into a rock. Sedimentary rocks can be identified by their layered appearance and will often have fossils in them. Examples: limestone, sandstone, coal
Metamorphic rocks are formed by both heat and pressure deep within the Earth’s surface. They can take up to millions of years to form! Like sedimentary rocks, they may have some layers but they will appear bent, curvy, or molted. Examples: marble, slate, schist
Earth recycles and reuses it’s rocks. Nothing is lost – it is just reformed. Through eorision, weathering, melting, cooling, and lots of pressure, old rocks are broken down and new rocks are formed. We call this type of recycling the Rock Cycle! Check out the diagram below!
Our novice geologists this month had a special appearance by paleontologist Dr. Neal Immega from the Houston Gem & Mineral Society. Dr. Immega taught the students about the rock cycle, let them examine a variety of rocks, and showed the students some really cool petrified turtle poop!
Questions: How well did you pay attention?
- What are the three types of rocks?
- How are each types of rock formed?
- Name at least two types of processes that change rocks into different rocks.
With your parent’s permission, research the following rock formations.
- The Arbol de Piedra, Bolivia
- Immortal Bridge, Mt. Tai, China
- Kannesteinen Vågsøy, Norway
- Giant’s Causeway, Northern Ireland
- Horseshoe Bend, Arizona, USA
- Painted Cliffs, Tasmania
- The Wave Rock, Arizona, USA
- Split Apple Rock, New Zealand
What types of rocks are they? How were they shaped in their current form? What type of processes did they undergo?