LET’S FIND OUT OUR DYNAMIC EARTH THE ROCK CYCLE SARA HOWELL Britannica Educational Publishing IN ASSOCIATION WITH ROSEN EDUCATIONAL SERVICES
A ROCKY HISTORY Millions of years ago Earth looked very different than it does today Over time rocks have been formed worn down and formed again This is called the rock cycle A cycle is a series of events or actions that repeat regularly There are several cycles in nature The seasons are a cycle The way water moves around Earth is called the water cycle Scientists can find clues to Earth’s past by studying how its rocks have changed or moved For example rocks Though rocks seem to be an unchanging and permanent part of Earth they are actually part of an endless cycle of change 4
Traces of extinct sea creatures such as this trilobite are a sign that land was once underwater can show us that large areas of land were once covered by thick layers of ice Layers of rock can show us how ancient earthquakes shaped mountains and valleys The tiny fossils of ocean creatures found in rocks can show us how some areas that are now dry land were once covered by water In fact the history of Earth can be told in rocks Vocabulary Fossils are the remains or traces of plants and animals that lived long ago 5
