The Rock Cycle6th Grade

Mrs. Boguslaw Inside the Restless Earth Chapter 2, Section 1

Rock

• A naturally occurring solid mixture of one or more minerals and organic matter

• Always changing

Uses of Rock• Early humans used rocks as hammers to make other tools

• Arrowheads, spearpoints, and knives were made from rocks like chert and obsidian

• Used for monuments, buildings, and roads

• Construction materials include granite, limestone, marble, sandstone, slate, and many other rocks

• Rock is also an important ingredient in concrete and plaster

Three Main Types• Igneous: forms when hot, liquid rock (magma)

cools and solidifies

• Metamorphic: forms when the structure, texture, or composition of a rock have changed because of heat and pressure

• Sedimentary: forms when sand grains are compacted and compressed and then cemented together to form a rock

Rock Cycle

• The series of processes in which a rock forms, changes from one type to another, is destroyed, and forms again by geological processes

Processes That Shape the Earth

• Certain geological processes make and destroy rock

• These shape our planet and influence the type of rock found in certain areas of the earth’s surface

Weathering

• The process in which water, wind, ice, and heat break down rock

• Breaks rock into fragments, which are the sediment from which sedimentary rock is made

Erosion

• The process by which wind, water, ice, or gravity transports soil and sediment from one location to another

Deposition

• The process in which material is laid down

• Sediment moved by erosion is dropped off and comes to rest

• Sediment may get pressed together and become sedimentary rock

Heat and Pressure• Sedimentary rock can form when buried sediment

is squeezed by the weight of the overlying layers of sediment

• If temperature and pressure are high enough at the bottom of the sediment, metamorphic rock can form

• Sometimes, the rock gets hot enough to melt, which forms magma. Magma eventually cools to become igneous rock.

How the Cycle Continues

• Buried rock reaches the earths surface by a combination of uplift and erosion

• Uplift: movement within the earth that causes rocks inside the earth to be moved to the surface

Rock Classification

• Three main classes (igneous, sedimentary, metamorphic)

• Each class can be divided further based on differences in how and where it forms

• Rocks are studied in detail based on two important criteria - composition and texture

Composition

• the chemical makeup of a rock; describes either the minerals or other materials in the rock

• Example: a rock that is made up of mostly quartz will have a very similar composition to quartz

Texture• the quality of a rock that is based on the sizes,

shapes, and positions of the rock’s grains

Igneous Rocks6th Grade

Mrs. Boguslaw Inside the Restless Earth Chapter 2, Section 2