Chapter 4 Rocks

What is a rock? A rock is a mixture of minerals, minerialoids, glass or organic matter.

Types of Rocks Sedimentary Igneous Metamorphic

How are rocks formed? Rocks are formed through a series of processes that transforms Earth materials back and forth from the three types of rocks. This process is called the rock cycle.

ROCK CYCLE Shows the three types of rock and they are formed. Factors involved in rock formation- weathering, erosion, heat, pressure Processes that form rock – compaction, cementation, melting, cooling Ever-changing processes moving from one type of rock to another.

IGNEOUS ROCKS Rocks that are formed either molten material from a volcano or from deep inside the Earth’s surface.

Two Types of molten material Lava Magma Both can reach temps of 1400 o C.

What is Lava? Lava- the molten material that reaches the Earth’s surface after a volcanic eruption. It is pushed to the surface due to intense heat and pressure. The outside air or water cools the materials forming rocks.

What is magma? Magma – molten material found beneath the Earth’s surface. Found about 60km to 200 km below the surface. Radioactive elements and intense pressure melts rocks forming magma. Less dense than the solid rock so it pushed to the surface.

Two types of igneous rock Intrusive – rocks that are formed from magma beneath the Earth’s surface. Extrusive – rocks that are formed when lava cools on or near the Earth surface.

Intrusive Igneous Rocks Formed from large mineral grains Are found when rock and soil are removed or when it pushed to the surface or forces in Earth have pushed them to the surface.

Extrusive Igneous Rocks Lava flows to the surface of the Earth and is cooled by air or moisture. Cools quickly so mineral grains are small. Typically fine-grained in texture.

Classification of Igneous Rocks Igneous rock is classified by the three magma that formed them. Three types of magma is basaltic, granitic, and andesitic.

Basic Igneous Rock Textures Fine – grained: Crystals too small to be seen without the unaided eye. Coarse- grained: Crystals large enough to be seen by the unaided eye Glassy: Brittle glossy crystals due to quick cooling. Porphyritic: Large crystals embedded in a cluster of small crystals.

Weathering Day-in and day-out influences of the atmosphere. Changing temperature, Wind, Humidity, and organic matter. Causes slow disintegration and rock decomposition.