Earth Rocks!

Earth Rocks!

Power hour 95

Earth Rocks! 

Earth is made of rocks. They can be small enough to fit in your hand or as big as a house. Rocks have different colors and textures. You know a rock when you see one-but can you identify the three basic groups of rocks? 

Rock Groups

Earth is a giant rock-making machine. Rocks form, break apart, and then form again. Read about the three groups of rocks, and look at examples of each. 

Sedimentary

Sedimentary rocks begin as sediment at the bottom of rivers, lakes, and oceans. Sediment is made of small pieces of sand, clay, and shells. The weight of water presses down on the sediment until it becomes hard. 

Igneous

Igneous rocks are created by heat. They start off as magma, which is hot, melted rock deep within a volcano. When magma cools and hardens, igneous rock forms. Igneous rock also forms when lava cools. Lava is magma that erupts from a volcano

Metamorphic

Metamorphic rocks start as igneous or sedimentary rocks. Heat and heavy pressure cause the rock to undergo a metamorphosis, or a change. The new rock often has a different color.

Multiple Choice

How many groups of rocks does the passage name?

• A. one

• B. three

• C. two