ROCKS

What is a Rock? Rocks are naturally occurring solid material made from one or more minerals. Rocks are classified based on the way they were formed. Three types of Rocks: Igneous – form when hot, liquid rock, or magma, cools and solidifies Sedimentary – formed by particles that have been carried or deposited and then compacted and cemented together. Metamorphic – rocks formed from chemical reactions one rock forms into another kind over long periods of time.

IGNEOUS ROCKS GRANITE BASALT CLIFFS GABBRO

Igneous Rocks Igneous rocks are classified according to their composition and texture. 4 basic types of textures Glassy – black and sharp Fine grained – interlocking pieces Coarse grained – consist of interlocking mineral crystals Porphyritic – made of large crystals scattered on the back of small crystals.

Igneous Rock Formations Extrusive – rock formed from lava Intrusive – rock formed when magma forces its way upward into preexisting rocks then hardens Magma – molten material below the earth’s surface. Lava – molten material above the earth’s surface.

Magma Rocks

SEDIMENTARY ROCKS LIMESTONE CHALK COAL

Sedimentary Rocks Sedimentary rocks are classified according to materials from which they are made. There are three types of sedimentary rocks

Clastic Sedimentary Rocks Formed form fragments of previously existing rock Classified according to size and shape of the fragments Examples: Conglomerate – made of pebbles and pebbles are smooth and rounded Sandstone – made of small sand-size grains (very common) Shale – made of particles smaller than sand

Organic Sedimentary Rocks Formed either directly or indirectly from material that was once living Examples: Limestone – made primarily of mineral calcite Chalk – form of fine-grained limestone composed of microscopic shells, small fragments of shells, and calcite crystals Coal – made from plants that lived million of years ago.

Chemical Sedimentary Rocks Formed by chemical means that do not involve living organisms Examples Halite and Gypsum

HOW ARE SEDIMENTARY ROCKS FORMED ?

METAMORPHIC ROCKS MARBLE SLATE GNEISS

How are Metamorphic Rocks Formed? Formed under tremendous heat, great pressure, and chemical reactions Metamorphism is changing one type of rock into another as a result of heat pressure and/or chemical reaction. Types of Metamorphic Rock: Foliated – mineral crystals are arranged in parallel layers or bands (ex. Schist, slate, and gneiss) Nonfoliated – rocks are not banded and do not break into layers (ex. Marble and quartizite)

HOW ARE METAMORPHIC ROCKS FORMED ?

The rock cycle is the continuous changing of rocks from one kind of rock to another over long periods of time. Matter from the earth’s crust is changed from one form to another, but NONE is ever lost.