 Objectives:  1. Identify three types of rocks  2. Explain how one type of rock can change into another.  3. Tell how common each rock type is in Earth’s crust.

Rocks Are Made of Minerals AA rock is a naturally formed solid that is usually made up of one or more types of minerals. TThe structure of rocks is different from that of minerals. AA mineral is always made up of the same elements in the same proportions. TThe proportion of different minerals in a particular rock my vary. LLimestone can be composed of entirely one mineral (calcite) OObsidian and coal contains no minerals CCoal is made up of the remains of ancient plants that have been buried and pressed into rocks

Our World is Built on Rocks  Rocks can be used for many different purposes such as  1. The building of houses and skyscrapers  2. The sources of metals, such as iron, aluminum and copper  3. The carving of statues and other works of art  4. The base for pavement for roads and highways  People value rocks because they last a long time and some are beautiful  People study rocks to learn how areas have changed through time.

RRocks do change, but the changes usually take thousands to millions of years. TThe rock cycle is the set of natural process that form, change, break down and re- form rocks. AA cycle is made up of repeating events that happen one after another. RRocks do not move through the rock cycle in any particular order. AA rock at any point in the cycle can change in 2 or 3 different ways. TThe rock cycle has no beginning or end but goes on continuously

ROCK CYCLE

Rock Types There are three types of rocks and they are classified by how they form. 1. Igneous Rock 2. Sedimentary Rock 3. Metamorphic Rock

 Igneous rock forms when molten rock cools and becomes a solid.  Igneous rocks may form within Earth or on Earth’s surface  Igneous rocks that originally formed at great depths can reach Earth’s surface  Deep rocks may be raised when mountains are pushed up.  Other processes also wear away the rocks that cover the deeper rocks.

Sedimentary Rocks SSedimentary rock forms when pieces of older rocks, plants, and other loose material become pressed or cemented together. LLoose material carried by water or wind and then settle out to form layers. TThe lower layers can be pressed into rock by the weight of the upper layers. AAlso, new minerals can grow in the spaces within the material (sediment) cementing it together.

Metamorphic Rocks Metamorphic rock forms when heat or pressure cause older rocks to change into new types of rock. A rock can get buried deep in the crust where pressure and temperatures are great These conditions cause the structure of the rock to change new minerals grow in place of the original minerals Metamorphic rocks can also be raised to the Earth’s surface over time.

Rocks in the Crust Igneous, Sedimentary and Metamorphic rocks are all found in the Earth’s crust Most of the Earth’s crust consists of igneous and metamorphic rock (95%) Sedimentary rock only makes up 5% of Earth’s crust Sedimentary rocks are most common at the surface because they are formed by processes that occur at the surface of the Earth. Most igneous and metamorphic rocks are formed by processes that occur deeper within Earth.