Rocks and the Rock Cycle Three Rock Types Igneous Rocks Sedimentary Rocks Metamorphic Rocks All rock types are interrelated through the rock cycle. Reference: Tarbuck and Lutgens Pages 34 - 51

Igneous Rocks An igneous rock is formed when magma or lava cools and solidifies

Igneous Rocks Formed by the cooling and hardening of hot molten rock. If the molten rock is located within Earth it is called magma. If the molten rock reaches the surface and exits through volcanoes, it is then referred to as lava. Two classifications of Igneous rock; 1) Plutonic (intrusive) – forms from magma. 2) Volcanic (extrusive) – forms from lava.

Molten rock Igneous Rocks in the Earth is magma Magma is buoyant, rises to surface, & sometimes breaks through when magma reaches Earth’s surface it is called lava

Igneous Rocks Why should we care? Igneous rocks make up bulk of Earth’s crust Earth’s mantle is basically one huge igneous rock Important rocks economically Striking landscape features

Igneous Rocks Igneous rocks that form - at the surface are volcanic (extrusive) Igneous rocks that form - deep down are plutonic (intrusive)

Plutonic rocks To see them, they must be uplifted to surface Igneous Rocks Plutonic rocks To see them, they must be uplifted to surface And softer surrounding rock eroded away Magma body

Igneous Rocks Plutonic rocks For us to ever see them, they must be uplifted to the surface And softer surrounding rock eroded away

Plutonic igneous rock example: El Capitan Igneous Rocks Yosemite Nat. Park, California

As magma cools, atoms arrange in an orderly crystal structure Igneous Rocks As magma cools, atoms arrange in an orderly crystal structure crystallization

Igneous Rocks Note: different crystal sizes

Igneous Rocks Coarse-grained igneous rock Close up of crystals Note the variety of crystal sizes

Sedimentary Rocks Rock formed when the weathered products of pre-existing rocks have been transported, deposited, and compacted or cemented into solid rock. Usually formed in marine (water) environments where sediment is deposited by streams and rivers. Most of Earth’s crust (95%) is igneous rock but the surface is covered by sedimentary rocks. Three classifications of Sedimentary Rocks; 1) Clastic (Detrital) - Fragments 2) Chemical - precipitation and evaporation 3) Organic – once living material 4) Biochemical

Metamorphic Rocks Rock formed below Earth’s surface when pre-existing rock is altered by heat, pressure, and chemically active fluids. Metamorphism changes rocks in size, shape, texture, and the minerals they contain. Metamorphism varies in degree from; High Grade. Ex. Granite changes to Gneiss. Low Grade. Ex. Shale changes to Slate.

Rock Cycle Magma Metamorphic Igneous (Volcanic) (Plutonic) Melting Magma Cool & Crystallize Metamorphic Igneous (Volcanic) (Plutonic) Heat & Pressure Weathering & Erosion Sedimentary (Clastic) (Chemical) (Organic) Compaction & Cementing Sediment Sand, Silt, & Clay

Rock Cycle Magma Metamorphic Igneous (Volcanic) (Plutonic) Melting Magma Cool & Crystallize Melting Metamorphic Igneous (Volcanic) (Plutonic) Heat & Pressure Weathering & Erosion Heat & Pressure Weathering & Erosion Sedimentary (Clastic) (Chemical) (Organic) Weathering & Erosion Compaction & Cementing Sediment Sand, Silt, & Clay

Sample Problem In the diagram below, rock types/materials are indicated by numbers and processes are indicated by letters. Indicate the rock types/materials and processes for the rock cycle diagram by completing the table below. Answer: A 1. Magma E 2. 5. B D Weathering & Erosion C 3. 4. Rock Type / Materials Process 1. Magma A Cool & Crystallize 2. Igneous B Weathering and Erosion 3. Sediments C Compacting & Cementing 4. Sedimentary D Heat & Pressure 5. Metamorphic E Melting