Rocks

The Rock Cycle: 

The Rock Cycle The continuous processes that cause rocks to change Caused by interactions among the earth’s water, air and land causes these changes.

Fig. 2.9: 

Fig. 2.9 MAGMA

Slide 4: 

MAGMA Crystallization IGNEOUS

Slide 5: 

MAGMA IGNEOUS Plutonic Crystallization

Slide 6: 

MAGMA Volcanic IGNEOUS Plutonic Crystallization

Slide 7: 

MAGMA Volcanic IGNEOUS Plutonic Uplift Crystallization Weathering

Slide 8: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT Uplift Crystallization Weathering SEDIMENT

Slide 9: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

Slide 10: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

Slide 11: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Crystallization Weathering Erosion Transport Deposition

Slide 12: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition Can you see any shortcuts?

Slide 13: 

MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition

The Major Rock Groups: 

The Major Rock Groups Igneous Formed from the melting of molten rock Plutonic (intrusive):slow cooling and crystallization Volcanic (extrusive): quick cooling at the surface Sedimentary Formed at the Earth’s surface Clastic (Mineral Fragments or grains, clays) Chemical (crystalline chemical/biochemical precipitates) Metamorphic Changed by elevated pressure and temperature.

Igneous Rocks: 

Igneous Rocks Called the “Fire Rocks” Intrusive Igneous rocks are formed as trapped magma cools beneath the Earth’s surface. Extrusive Igneous rocks are formed above the ground when volcanoes erupt and the magma cools.

Comparison of Intrusive/Extrusive: 

Comparison of Intrusive/Extrusive

Classification of Igneous Rocks: 

Classification of Igneous Rocks Texture Appearance of an igneous rock based on size, shape and arrangement of interlocking crystals Composition Based on the portions light and dark minerals in the rock.

Classification of Major Igneous Rocks: 

Classification of Major Igneous Rocks

Phaneritic Texture: 

Phaneritic Texture Phaneritic or Coarse-Grained If magma cools slowly, ions can move larger distances toward the fewer centers of crystal growth. Slow cooling results in the formation of large crystals. Granite Diorite Gabbro Peridotite

Aphanitic Texture : 

Aphanitic Texture Aphanitic or Fine-Grained If magma cools quickly, ions lose their motion and combine quickly. Rapid cooling results in rocks with small, interconnected mineral grains. Rhyolite Andesite Basalt

Porphyritic Texture: 

Porphyritic Texture Crystallization from magma does not always occur at the same rate or at the same time. Some crystals may become large before others start to form. This results in rock with large crystals called phenocrysts surrounded by fine-grained minerals. Porphyritic Basalt Porphyritic Andesite

Glassy Texture: 

Glassy Texture In some lava flows there may not be enough time for ions to arrange into a network of crystals before cooling. The rocks produced have randomly distributed ions with no crystalline structure. Obsidian Basaltic Glass

Vesicular Texture: 

Vesicular Texture Also called Frothy Glass Similar to glassy texture having no crystalline structure. Characterized by being pitted with cavities or vesicles that are occur when gas bubbles are present in the magma. Pumice Scoria

Pyroclastic Texture: 

Pyroclastic Texture Relatively soft, porous rock that is formed from volcanic ash and dust that is released into the atmosphere from volcanic activity. Volcanic ash and dust compact and cement together to form the rock. Volcanic Tuff Tuff from California 18.5 million yrs. old

Classification of Major Igneous Rocks: 

Classification of Major Igneous Rocks

Felsic Composition: 

Felsic Composition Also known as Granitic composition. Composed mainly of the light-colored silicate minerals quartz and feldspar. Major rocks of the continental crust. Rhyolite is an extrusive felsic rock. Granite Pegmatite Granite Rhyolite

Intermediate Composition: 

Intermediate Composition Also known as Andesitic composition. Contain at least 25% dark silicate minerals such as amphibole, pyroxene, and biotite mica. Another dominant mineral is plagioclase feldspar. Andesite Diorite

Mafic Composition: 

Mafic Composition Also known as Basaltic composition. Contain dark silicate minerals and plagioclase feldspar. Rich in the elements magnesium and iron which makes them darker and denser. Gabbro Basaltic glass Scoria Basalt

Ultramafic Composition : 

Ultramafic Composition Rich in the elements iron and magnesium. Contains mostly the minerals olivine and pyroxene and less than 45% silicate minerals. Rare at the Earth’s surface, but much of the upper mantle is made of Peridotite. Peridotite Dunite Komatiite

Sedimentary Rocks: 

Sedimentary Rocks Latin meaning “settling” Form when solids settle out of water or air. After being deposited, the sediments are turned into rocks. Compaction squeezes or compacts sediments. Cementation occurs when minerals are deposited in the tiny spaces between the sediments.

Classification of Sedimentary Rocks: 

Classification of Sedimentary Rocks Clastic Sedimentary Composed of weathered bits of rocks and minerals. Classified by particle size Chemical or Biochemical Sedimentary Form when dissolved substances precipitate, or separate, from water.

Classification of Major Sedimentary Rocks: 

Classification of Major Sedimentary Rocks

Clastic Texture: 

Clastic Texture The most common minerals are quartz and feldspar. Grouped according to size of the sediments. Conglomerate has rounded , gravel-size particles. Breccia has angular, gravel-size particles. In Sandstone most of the particles are sand-size grains. Conglomerate Breccia Sandstone

Clastic Texture: 

Clastic Texture Arkose has small-grained sediments composed of quartz and feldspar. Siltstone has fine-grained sediments composed of quartz and clay minerals. Claystone is also composed of quartz and clay minerals, but they are very fine-grained . Arkose Siltstone Claystone

Chemical Texture: 

Chemical Texture Forms when dissolved substances precipitate out from a water solution. Usually occurs when water evaporates leaving behind a solid product. Chert is composed of silica or quartz. Dolostone is composed of dolomite. Rock Salt is composed of halite. Chert Dolostone Rock Salt

Biological Texture: 

Biological Texture Bituminous Coal is composed of densely compacted organic material. Approximately 90% of all Limestone is formed from biochemical sediments of calcite. Coquina is composed of shells and skeletal remains that settled to the ocean floor. Bituminous Coal Limestone Chalk Coquina Fossiliferous Limestone

Metamorphic Rocks: 

Metamorphic Rocks Means “to change form” Changes occur at elevated temperatures and pressures. Two ways change happens: Contact Metamorphism occurs when hot magma intrudes into rock - results in minor changes and low-grade metamorphism. Regional Metamorphism occurs during mountain building - results in large-scale deformation and high-grade metamorphism.

Agents of Metamorphism: 

Agents of Metamorphism Heat provides energy for the chemical reactions that cause existing minerals to recrystallize and allow new minerals to form. Pressure causes the spaces between mineral grains to close creating a compact rock with greater density.

Pressure or Stress as a Metamorphic Agent: 

Pressure or Stress as a Metamorphic Agent Forces are applied equally in all directions to buried rocks In mountain building, rocks are shortened in the direction that differential pressure is applied

Classification of Major Metamorphic Rocks: 

Classification of Major Metamorphic Rocks

Classification of Metamorphic Rocks: 

Classification of Metamorphic Rocks Classified mainly by texture. Foliated Metamorphic rocks have a layered or banded appearance. Gneiss is an example. Nonfoliated Metamorphic rocks do not have a banded texture and usually contain only one mineral. Marble is an example . Gneiss Marble

Foliated Metamorphic Rock: 

Foliated Metamorphic Rock Slate Mudstone Phyllite Mudstone Schist Slate Amphibolite Basalt or Gabbro Gneiss Schist

How Sedimentary Shale becomes Foliated Metamorphic Gneiss: 

How Sedimentary Shale becomes Foliated Metamorphic Gneiss

Nonfoliated Metamorphic Rock: 

Nonfoliated Metamorphic Rock Metaconglomerate Conglomerate Marble Limestone Quartzite Sandstone Anthracite Coal Bituminous Coal

In Summary…: 

In Summary…