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The Rock Cycle

Ag Earth Science – Chapter 3.1 3.1 Vocabulary

mineral A natural occurring, inorganic crystalline material with a unique chemical composition.

rock A consolidated mixture of minerals

igneous rock A rock formed by the crystallization of molten magma

sedimentary rock Rock formed by from weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented.

metamorphic rock Rock formed by the alteration of preexisting rock deep within the Earth by heat, pressure, and/or chemically active fluids.

rock cycle A model that illustrates the origin of the three basic rock types and the interrelatedness of Earth materials and processes.

magma A body of molten rock found at depth including any dissolved gases and crystals.

lava Magma that reaches the Earth’s surface.

weathering The disintegration and decomposition of rock at or near the Earth’s surface.

sediments Loose particles created by weathering and erosion of rock, by chemical precipitation from solution in water, or from the secretions of organisms and transported by water, wind, or glaciers.

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Rocks A rock is any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet. Rocks are classified into 3 major types Igneous Rocks   Sedimentary Rocks Metamorphic Rocks

The Rock Cycle Interactions among the Earth’s water, air, and land can cause rocks to change from one type to another The continuous processes that cause rocks to change make up the rock cycle When magma (molten material beneath the Earth’s surface) cools and hardens, igneous rocks form. Magma that reaches the surface is called lava.   When weathered (process by which rocks are physically and chemically broken down into small pieces called sediments) sediments are compacted and cemented together, they form sedimentary rocks. When sedimentary rocks are subjected to extreme pressure and heat, they change in metamorphic rock.

The Rock Cycle

Powers of the Earth’s Rock Cycle Heat from the Earth’s interior are responsible for forming both igneous and metamorphic rocks Weathering and the movement of weathered materials are generated by the sun’s energy and produce sedimentary rock.

Another Dam Photo …..

Ag Earth Science – Chapter 3.2 3.2 Vocabulary

ignis Latin word for “fire”

intrusive igneous rock Igneous rock that formed below the Earth’s surface

extrusive igneous rock Igneous rock that has formed on the Earth’s surface

porphyritic texture An igneous texture consisting of large crystals embedded in a matrix of much smaller crystals

granitic composition A compositional group of igneous rocks that indicate a rock is composed entirely of light-colored silicates, mainly quartz and feldspar

basaltic composition A compositional group of igneous rocks indicating that the rock contains substantial dark silicate minerals and calcium-rich plagioclase feldspar

andesitic composition A composition of igneous rock rocks lying between felsic and mafic

ultramafic Igneous rock composed mainly of iron and magnesium-rich minerals

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Formation of Igneous Rocks Igneous – Comes from the Latin word “ignis” which means “fire”

Formation of Igneous Rocks Intrusive Igneous Rocks – rocks that form when magma hardens (cools) beneath the Earth’s surface. Example – Granite

Formation of Igneous Rocks Extrusive Igneous Rocks – rocks that form when lava hardens (cools) above the Earth’s surface. Example – Rhyolite

Classification of Igneous Rocks Texture and composition are two characteristics used to classify igneous rocks.

Classification of Igneous Rocks Course Grained Texture – Slow cooling = large crystals. Large crystals exhibit “course-grained” texture.

Classification of Igneous Rocks Fine Grained Texture – Rapid cooling = small mineral grains. Small grains are said to have “fine-grained” texture.

Classification of Igneous Rocks Glassy Texture – Lava spews on surface = may not be time for ions to arrange themselves into crystals. Random distributed ions = glassy texture.

Classification of Igneous Rocks Porphyritic Texture – Large body of magma may take thousands of years to harden. Variety of temperature/cooling within large mass = large crystals and fine-grained minerals.

Classification of Igneous Rocks Granite Composition – Made almost entirely of light colored silicate minerals quartz and feldspar.

Classification of Igneous Rocks Basaltic Composition – Rocks that contain many dark silicate minerals and plagioclase.

Classification of Igneous Rocks Andesitic Composition – In-between granite (light) and basaltic (dark) compositions.

Classification of Igneous Rocks Ultramafic – Composed almost entirely of dark silicate minerals (peridotite).

Classification of Igneous Rocks

That’s Random

Ag Earth Science – Chapter 3.3 3.3 Vocabulary

erosion The incorporation and transportation of material by a mobile agent such as water, wind, or ice.

deposition The process by which an agent of erosion loses its energy and drops the sediment it is carrying.

compaction Process by which sediments are squeezed together by the weight of overlying materials driving out water.

cementation Solidification of sediments by deposition of dissolved minerals

clastic sedimentary rock A sedimentary rock made of broken fragments of existing rock

chemical sedimentary rock Sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means

Formation of Sedimentary Rocks Sedimentary – Comes from the Latin word “sedimentum” which means “settling”

Formation of Sedimentary Rocks Weathering, Erosion, and Deposition   Erosion – involves weathering and the removal of rock When an agent (wind, ice, water, or gravity) loses energy, it drops the sediments. Deposition – the process of erosion losing energy and dropping sediment.

Formation of Sedimentary Rocks Compaction and Cementation Compaction – process of “squeezing” or compacting sediments Cementation – dissolved minerals are deposited in the tiny spaces among sediments.

Formation of Sedimentary Rocks The 5 Main Processes that Form Sedimentary Rocks   weathering erosion deposition compaction cementation

Classification of Sedimentary Rocks Clastic Sedimentary Rocks – Made up of weathered bits of rocks and minerals

Classification of Sedimentary Rocks Classified according to particle size   Conglomerate –(gravel) rounded, large gravel-size or larger pebbles cemented together Breccia – (gravel) angular particles Sandstone – sediments are sand-sized grains Siltstone – fine-grained sediments

Classification of Sedimentary Rocks Chemical and Biochemical Sedimentary Rocks – form when dissolved substances precipitate, or separate, from water solution. Examples – limestones, rock salt, chert, flint, and rock gypsum.

Features of Some Sedimentary Rocks The many unique features of sedimentary rocks are clues to how, when, and where the rocks formed. Each layer is a “time period” Fossils are unique in sedimentary rocks

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Ag Earth Science – Chapter 3.4 3.4 Vocabulary

metamorphism The changes in mineral composition and texture of a rock subjected to high temperatures and pressure within the Earth

contact metamorphism Changes in rock caused by the heat from a nearby magma body

regional metamorphism Metamorphism associated with large-scale mountain building

hydrothermal solution The hot, watery solution that escapes from the mass of magma during later stages of crystallization

Another Dam Photo …..

Formation of Metamorphic Rocks Metamorphism – “to change form” Formation of Metamorphic Rocks Most metamorphic changes occur at elevated temperatures and pressures. These conditions are found a few kilometers below the earth’s surface and extend into the upper mantle

Formation of Metamorphic Rocks Types of Metamorphism   Contact Metamorphism – Hot magma moves into rock Regional Metamorphism – large scale deformation and high-grade metamorphism due to extreme pressures and temperatures. (Example – mountain building)

Agents of Metamorphism The agents of metamorphism are heat, pressure, and hydrothermal solutions

Agents of Metamorphism Heat – Most important agent of metamorphism. Provides energy for chemical reactions. Heat comes from magma and change in temperature with depth.

Agents of Metamorphism Pressure (Stress) – Increases with depth (example – bottom of swimming pool). Pressure causes spaces between minerals to close = greater density.

Agents of Metamorphism Reactions to Solutions – solutions that surround mineral grains aid in recrystallization by making it easier for ions to move. When hot, water-based solutions escape from magma, they are called hydrothermal solutions. These hot fluids promote recrystallization.

Classification of Metamorphic Rocks The texture of metamorphic rocks can be foliated or nonfoliated

Classification of Metamorphic Rocks Foliated Metamorphic Rocks – a texture that gives the rock a layered appearance

Classification of Metamorphic Rocks Nonfoliated Metamorphic Rocks – a texture that does not exhibit a banded or layered appearance.

THE END ….. for this unit.