Rock Compostion

Rock – a naturally occurring solid mixture of one or more minerals or organic matter

Rocks are ALWAYS changing Rock cycle – the continual process by which new rock forms from old rock material

Early Uses of Rock Hammers Arrowheads Spear points Knives Scrapers

Types of Rock include: Granite Limestone Marble Sandstone Slate

Name some types of rock that have been used to construct buildings.

Certain geological processes make and destroy rock. The processes shape the features of our planet. These processes also influence the type of rock that is found in a certain area of Earth’s surface.

Weathering – the process in which water, wind, ice and heat break down rock

Weathering Breaks down rock into fragments Helps to create sedimentary rock

Erosion – the process by which sediment is removed from its source

Deposition – the process in which material is laid down

Turn to page 91 and read “Processes That Shape the Earth” in your textbook. Study the five steps listed that illustrate the rock cycle on page 92.

Igneous rock can change into sedimentary rock; metamorphic rock, or even back into igneous rock. As one rock type is changed to another type, several variables, including time, heat, pressure, weathering, and erosion may alter a rock’s identity. The location of the rock determines which natural forces will have the biggest impact on the process of change.

Scientists divide rock into three categories: igneous, sedimentary, and metamorphic. However, based on how and where the rock forms, further divisions can be made. Scientists study a rock’s composition and texture to classify it.

Composition – the chemical makeup of a rock; describes the minerals found in the rock

Texture – the quality of a rock that is based on the sizes, shapes, and positions of the rock’s grains

Igneous Rock

Igneous rock forms when hot, liquid rock, or magma, cools and solidifies.

3 ways Magma can form: When rock is heated When pressure is released When rock changes composition

Magma freezes between 700*C and 1,250*C.

The longer it takes for magma to cool, the more time crystals have to grow. The more time crystals have to grow, the larger the crystals are and the coarser the texture of the rock is. The less time it takes to cool, the less crystals will grow, resulting in a smoother rock.

Igneous rock, or magma, can form above or below the surface of Earth. What do we call an igneous rock formation that is above the surface of Earth?

Sedimentary Rock

Sedimentary rock forms at or near Earth’s surface. It forms without the heat and pressure that are involved in the formation of igneous and metamorphic rock.

Ways sedimentary rock form: Wind Water Ice Sunlight Gravity

Strata – layers of rock; the most noticeable feature of sedimentary rock.

Types of organic sedimentary rock: Fossils Coral Shells from sealife Coal

Metamorphic Rock

Metamorphic rocks are rocks in which the structure, texture, or composition of the rock have changed. All three types of rock can be changed by heat, pressure, or a combination of both.

Causes for Metamorphism Heat by nearby magma Built up pressure in Earth Collision of Earth’s crust Analogy examples: baking cookies or frying an egg What analogy can you think of?

Deformation – a change in the shape of a rock caused by a force placed on it. These forces may cause a rock to be squeezed or stretched.