CONTENTS Rocks minerals and fossils 4 The science of rocks and fossils 6 Working scientifically 7 Types of rocks 8 Rocks and water 10 Minerals and crystals 12 How hard 14 Weathering and erosion 16 Expanding ice 18 Making mountains 20 Volcanoes and earthquakes 22 How fossils form 24 Fossil puzzles 26 Reading your results 28 Glossary 30 Books and websites 31 Index and answers 32 Worlds in bold can be found in the glossary on page 30 A note about measurements Measurements are given in U S form with metric in parentheses The metric conversion is rounded to make it easier to measure
ROCKS MINERALS AND FOSSILS crust solid rock Rock is the natural substance that the Earth is made of On the Earth’s surface or crust rocks are mostly solid and hard The inside of the Earth is very hot at around 7,200 F 4,000 C and the rock here called the mantle is partly melted flint mantle partly melted rock outer core liquid iron inner core solid iron chalk basalt sandstone The Earth’s crust is made up of many types of rocks 4
MINERALS Rocks are made up of minerals Some rocks only contain one mineral Others contain mixtures of minerals A mineral is a pure natural substance from the ground This means it’s the same all the way through it’s not a mixture of different things Minerals include some metals such as iron and gold and gemstones such as diamonds and quartz Granite is a rock made up of a mixture of minerals including quartz feldspar and mica THE ROCK CYCLE Rivers and seas wear down rocks creating valleys and coastal cliffs Old rocks wear down crack apart and break up into sand dust and silt New rocks form from sand and mud on the seabed Volcanoes throw out lava melted rock which hardens to make new rock Earthquakes crush move and crack rocks This process of rocks breaking down and forming again is called the rock cycle A rock stone or pebble might seem like a very hard long-lasting object that doesn’t change much But over long periods of time Earth’s rocks change a lot ROCKS AND HUMANS Rocks are incredibly important to humans Besides living our whole lives on the Earth’s rocky crust we dig up all kinds of rocks and minerals to make many of the things we need FINDING FOSSILS Rocks also hold a record of life in the past in the form of fossils Fossils are made when rocks form around the remains or imprints of living things Over time the animal or plant material is replaced by rocks and minerals but the shape of the creature can still be seen This is a fossilized trilobite a type of animal that lived from around 520 million to 250 million years ago 5
