ROCKS what is a rock Let’s rock and roll Rocks make up every continent mountain and island on the planet But what is rock In simple terms a rock is a naturally occur ring solid object usually made from minerals Rocks are classified as one of three main types igneous sedimentary and metamorphic depending on how they’re formed A rock can also transform from one type to another over millions of years the processes of the rock cycle break it down or melt it change it and reform it into new rock MINERALS MATTER Within the three different categories of rocks what makes one rock different from another are the ways the different minerals combine together Rocks are usually made up of one or more minerals see page 100 to learn more about minerals Minerals are made up of tiny particles called atoms and these atoms are arranged in a particular particular pattern This pattern creates what are called crystals The crystals determine what a mineral looks like and they can shape how a rock looks too These crystals can affect whether a rock is rough or smooth and how hard it is Minerals also come in different different colors and that can affect a particular rock’s appearance too A mineral called hematite can make a rock red or brown It’s this mineral that gives sandstone sandstone its brown tint The mineral quartz gives rocks a range of colors though they usually tend to be light shades of gray Dacite usually bluish gray or pale gray is one rock that is often loaded with quartz 8
ROCK GLOSSARY Rocks and minerals may look simple but there’s a mountain of science that helps explain how they form and what they can do To make sure you’re on solid ground as you navigate the terrain take a minute to familiarize yourself with these important terms ATOMS Microscopic particles that are the basic unit of an element BACTERIA Single-celled microorganisms thought to be the first forms of life on Earth CONDUCTOR A material that transmits a form of energy such as heat or electricity some substances are better conductors than others CRYSTAL The arrangement of tiny parti cles called atoms and molecules found in minerals each mineral has its own crystal structure DORMANT Referring to a volcano that has not erupted in a long time but might again someday ELEMENT One of more than 100 sub stances on Earth that has a unique set of chemical and physical properties and that make up everything on the planet EROSION The natural process through which wind water and ice wears away and removes rock and soil EXTINCT In geology refers to a volcano that no longer erupts FOSSIL The remains of ancient life forms or traces or impressions of an organism which are found in rocks FRACTURE The way that minerals and rocks break apart or have a break within LANDFORM A natural feature of Earth’s surface such as a mountain LUSTER The way light reflects off a rock or mineral which indicates how dull or brilliant it is MOLTEN Turned into liquid by high heat MONOLITH A single giant stone or rock NUCLEAR Referring to the center or nucleus of an atom PROPERTIES The particular traits of a specific rock or mineral QUARRY A place from which large amounts of certain rocks are or have been removed often for use in buildings or the act of removing the rocks RADIATION A form of energy released by some elements as they naturally change that can be harmful in large doses materials with high levels of radiation are called radioactive SEDIMENT Broken pieces of rock that can move from one place to another and often settle to the bottom of bodies of water TECTONIC Relating to the structure of Earth’s crust and mantle and the activity that takes place within them VITREOUS A luster with a glassy look VOLCANOLOGIST A geologist who specializes in the study of volcanoes 9 Rocks
THE ROCK CYCLE GOING ROUND AND ROUND A bicycle made of stone Not quite The rock cycle is the name for the process that describes how rocks form and change into different types of rocks over time Rocks can form at any point in the cycle STORMY WEATHER Rocks on Earth’s surface are broken into tiny pieces by wind rain and ice during a process called weathering The pieces are called sediment and they are carried by water wind and ice and slowly pile up This step in the cycle is called erosion and deposition TURN TO STONE Loose sediment collects in one spot and is compressed or cemented together to form new rocks called sedimentary rocks This step in the cycle is called lithification THE BIG SQUEEZE Rocks on Earth’s surface are pushed underground at places where tectonic plates meet you’ll learn more about these plates on page 16 Heat and pressure within the planet create new rocks that are called metamorphic This step is called tectonic action 10
Rocks The Rock Cycle UNDERGROUND ACTION Deep below Earth’s surface extreme heat turns minerals into a liquid called magma Some cools slowly below Earth’s surface forming what are called intrusive or plutonic igneous rocks Other magma reaches the surface and becomes the lava produced by a volcanic eruption The lava cools quickly forming extrusive or volcanic igneous rocks 11
