Rocks

Chapter 4

What is a rock?

Rock Mixture of minerals, rock fragments, volcanic glass, organic material, or other natural materials.

What is a rock?

Rock Cycle Cycle that demonstrates the three types of rock and the processes that create and change them.

What is a rock?

Matter and the Rock Cycle

Changes that occur in the rock cycle never create or destroy matter. Elements that form the rocks are

simply redistributed.

Formation of Igneous Rocks

Igneous Rocks

Form when magma cools and hardens.

Formation of Igneous Rocks

Magma Forms when heat and pressure in the interior of the earth melt rock. Temps of magma range from 650

to 1200 degrees Celsius Because magma is less dense

than surrounding solid rock it is forced upward.

Magma that has erupted to the surface of the earth is called lava.

Formation of Igneous Rocks

Intrusive Rocks

Igneous rocks that form beneath the surface of the earth. Cool very slowly which results

in large mineral grains (coarse-grained).

Formation of Igneous Rocks

Extrusive Rocks

Form when lava cools on the surface of the earth. Cool rapidly resulting in small

mineral grains (fine-grained). Volcanic glass is a type of

extrusive igneous rock with no to few mineral grains

Very rapid cooling

Classifying Igneous Rocks Classification Classified as intrusive or

extrusive Classified into three families

based on composition of magma from which they formed. Basaltic Granitic Andesitic

Classifying Igneous Rocks Basaltic

Rocks

Dark-colored, dense Form from magma low in

silica and high in magnesium and iron Examples: Hawaii, moon

Classifying Igneous Rocks Granitic

Rocks

Light-colored, lower density Form from magma rich in

silica

Classifying Igneous Rocks Andesitic

Rocks

Form from magmas in between felsic (granitic) and mafic (basaltic).

Metamorphic Rocks Metamorphi

c Rocks

Rocks that have been changed by high temperature, high pressure, or hot fluids. The rock from which the

metamorphic rock formed is called the parent rock.

Classifying Metamorphic Rocks

Classification

Classified according to mineral composition and texture. Foliated

Mineral grains of the rock are arranged in parallel layers.

Nonfoliated Mineral grains of the rock are

not arranged in layers.

Formation of Sedimentary Rocks

Formation of Sedimentary Rocks

Form when sediments are pressed and cemented together or when minerals form from solution. Sediments are loose materials

such as rock fragments, mineral grains, and organics (bits of shell, etc).

Come from rock that has been eroded.

Classifying Sedimentary Rocks

Classification Classified by the type of sediments in the rock and how the rock formed. Detrital Chemical Organic

Detrital Sedimentary Rocks

Formation

Formed from pieces of other rock that have been compacted or cemented together. When exposed to the air, water,

and wind rock is broken down through the process of weathering.

Sediments can be moved through erosion to new locations where they are deposited.

Detrital Sedimentary Rocks

Compaction

As sediments are deposited, sediment layers on top put pressure on sediment layers below them, eventually pressing the sediments into rock.

Detrital Sedimentary Rocks

Cementation

As water moves through rocks, minerals are dissolved in the water.

The water carries the dissolved minerals through cracks in rock.

These minerals (such as quartz, calcite, or hematite) can be deposited between pieces of sediment, cementing them into rock.

Detrital Sedimentary Rocks

Further classification

Detrital sedimentary rocks are further classified by the shape and size of sediments that form them.

Chemical Sedimentary Rocks

Formation

Form when dissolved minerals come out of solution. Limestone

Calcium carbonate is dissolved in ocean water and precipitates out as calcite, forming limestone.

Rock Salt Water rich in salts leave the mineral

halite when the water evaporates, forming deposits of rock salt

Organic Sedimentary Rocks

Formation Rocks that are made from the remains of once living things Fossil-rich limestone Chalk

Consists of microscopic shells. Coal

Formed from plant remains buried in swamps.

The plant remains are changed into coal by microscopic organisms and pressure.