Chapter 2, Section 1 Rocks: Mineral Mixtures

Facts

A Rock is a solid mixture of crystals of one or more minerals.

Rocks can be classified by observing their characteristics and properties

What are some characteristics of rocks?

The Uses and History of Rocks

Early humans used rocks as tools. Some rocks were used as hammers, while others were used to sharpen rocks into sharp tips that could be used for arrows, knives, and scalpels

Rocks have been used in architecture in the past as well as in the present. Examples: granite, marble, sandstone, and slate

Rocks can help scientists answer questions about our Earth and solar system

Fossils found in rocks allow scientists to learn more about evolution and about the history of the Earth

What are some other uses of rock?

The Rock Cycle

The rocks in the Earth are constantly changing their shape and composition. This process is known as the rock cycle.

The way a rock changes determines its type. There are 3 main types of rocks: igneous, sedimentary, and metamorphic

The Rock Cycle SEDIMENTARY ROCK: grains of sand and sediment erode from the mountain and wash down into a water body. Overtime as the layers build up, they are pressed into a cement-like form.

Formation of Sedimentary Rock

The Rock Cycle METAMORPHIC ROCK: when pieces of the Earth collide, sometimes large pieces of rock are forced downward. The sedimentary rock changes state due to the intense heat and pressure

Formation of Metamorphic Rock

Metamorphic Rock

The Rock Cycle MAGMA: when metamorphic rock completely or partially melts.

Magma

The Rock Cycle IGNEOUS ROCK: Rock that forms as the magma rises to the Earth’s crust and cools

Formation of Igneous Rock

Igneous Rock

The Rock Cycle SEDIMENT: When igneous rocks on the Earth’s crust begins to erode, it breaks down into grains of sand and clay

Sediment

Classifying Further

The 3 types of rock can be classified further based upon their characteristics

Rocks can be classified based upon their composition. The composition of a rock is determined by the minerals that make up that rock

Rocks can also be classified by their texture. The texture of a rock is created based upon the sizes of the grains it contains

fine-grained: contains small particles medium-grained: contains average sized particles coarse-grained: contains large particles that are easily visible

Fine-Grained texture

Medium-Grained texture

Coarse-Grained texture

Composition/Texture of Igneous Rock The amount of time it takes for magma or lava to cool determines the texture of igneous rock FELSIC- lighter colored and less dense. Rich in silicon, sodium, aluminum, potassium MAFIC- dark colored and more dense. Rich in iron, magnesium and calcium

IGNEOUS ROCK FORMATIONS INTRUSIVE – when magma cools beneath Earth’s surface Ex. Plutons- large balloon shaped structures formed in deep areas EXTRUSIVE-igneous rock formed at the Earth’s surface Ex. Volcanic rock

SEDIMENTARY ROCK Formed at or near Earth’s surface without the heat and pressure.. Layers are deposited and compacted together. Layers of sedimentary rock are known as STRATA. The way in which layers are formed is called STRATIFICATION, or layering Sedimentary rock is classified by the way it is formed

Classification of Sed Rocks 1. CLASTIC- made from fragments of rocks and other minerals 2. CHEMICAL- forms from solutions of minerals and water 3. ORGANIC- forms from the remains of once living things

METAMORPHIC ROCK How does the rock change? CONTACT METAMORPHISM- occurs when rock comes in contact with magna and changes the surrounding rock REGIONAL METAMORPHISM- occurs when a lot of pressure builds up or when large pieces of the earth collide

TEXTURE OF MET ROCK FOLLIATED- has mineral grains that are aligned by pressure. Ex. Shale changed into slate, then phyllite, etc NONFOLLIATED- does not have a regular pattern of how the minerals are arranged Ex. Sandstone changed to quartzite