Rocks Rocks

Rocks v.s. Minerals RocksMinerals 1. Can be organic1. Inorganic 2. Mixture 2. Element or compound compound 3. Size and shape is3. Fixed in definite determined by the crystal patterns determined by the crystal patterns minerals within and minerals within and their cooling rates their cooling rates

Rocks  Made of two or more different minerals that have been: cemented together cemented together squeezed and heated together squeezed and heated together melted and cooled together. melted and cooled together.

Types of Rocks Igneous—born of fire Igneous—born of fire Sedimentary—made of leftovers Sedimentary—made of leftovers Metamorphic—result from heat and pressure Metamorphic—result from heat and pressure

8 processes that show how one rock changes into another: weathering weathering erosion erosion compaction compaction cementation cementation melting melting cooling cooling heat heat pressure pressure Sedimentary Rocks Igneous Rocks Metamorphic Rocks

Igneous Rocks

Intrusive igneous rocks are produced deep underground by the slow cooling and hardening of magma. This slow process allowed large crystals to form creating a very coarse rock. Intrusive igneous rocks are produced deep underground by the slow cooling and hardening of magma. This slow process allowed large crystals to form creating a very coarse rock. Extrusive igneous rocks cool at or above the surface much more quickly so only small crystals if any form—sometimes there are holes where the gases escaped. These rocks are small grained or smoother in texture. Extrusive igneous rocks cool at or above the surface much more quickly so only small crystals if any form—sometimes there are holes where the gases escaped. These rocks are small grained or smoother in texture. Porphyry is a rock that begins to cool under ground and then an event forces it to the surface where it rapidly finishes cooling. It shows both large and fine grains. Porphyry is a rock that begins to cool under ground and then an event forces it to the surface where it rapidly finishes cooling. It shows both large and fine grains. Igneous Rocks

Formed From… Magma = molten material beneath Earth’s crust. crust. Lava = molten material on the surface of Earth’s crust. Earth’s crust.

Classification of Igneous Rocks Composition-refers to the minerals that make up the rock Composition-refers to the minerals that make up the rock Texture-shape, size, arrangement and distribution of minerals that make up the rock Texture-shape, size, arrangement and distribution of minerals that make up the rock

Composition Extrusive- Formed from lava; volcanic Extrusive- Formed from lava; volcanic Intrusive- Formed deep within the earth Intrusive- Formed deep within the earth Obsidian Pumice Granite Gabbro Basalt

Textures Glassy Glassy Fine-grained Fine-grained Coarse-grained Coarse-grained Porphyritic Porphyritic ObsidianGranite Basalt

Granitic – light colored, low density, rich in oxygen and silicon, made from thick, sticky felsic lava Granitic – light colored, low density, rich in oxygen and silicon, made from thick, sticky felsic lava White Granite Red Granite Examples

2. Classification based on mineral composition Basaltic Basaltic Granitic Granitic Andesitic Andesitic

Basaltic – dark colored, high density, rich in iron and magnesium, made from thin, runny mafic lava Basaltic – dark colored, high density, rich in iron and magnesium, made from thin, runny mafic lava Examples Examples BasaltScoria

Andesitic – mineral compositions in between basaltic and granitic, made from lava in between basaltic and granitic Andesitic – mineral compositions in between basaltic and granitic, made from lava in between basaltic and granitic DioriteAndesite Examples

James Hutton Suggested that the Earth was much older and that processes occurring in the present were the same processes that had operated in the past, and would be the processes that operate in the future. Suggested that the Earth was much older and that processes occurring in the present were the same processes that had operated in the past, and would be the processes that operate in the future. This concept became known as uniformitarianism and can be summarized by the phrase "the present is the key to the past" This concept became known as uniformitarianism and can be summarized by the phrase "the present is the key to the past"

Sedimentary Rocks Formed from the breaking apart — weathering—of other rocks (igneous, metamorphic, or sedimentary) and the cementation, compaction and Formed from the breaking apart — weathering—of other rocks (igneous, metamorphic, or sedimentary) and the cementation, compaction and of these broken pieces or sediments. of these broken pieces or sediments. May contain other material May contain other material such as shells, bones or such as shells, bones or fossils. In igneous, fossils fossils. In igneous, fossils would melt, in metamorphic would melt, in metamorphic they be crushed so the only they be crushed so the only family with fossils is sedimentary. family with fossils is sedimentary.

Classification of Sedimentary Rocks Clastic Rocks- Made of the fragments of previously existing rocks, compressed or compacted together—iron or quartz may be “glue” Clastic Rocks- Made of the fragments of previously existing rocks, compressed or compacted together—iron or quartz may be “glue” Organic Rocks- Come from organisms or materials that have lived Organic Rocks- Come from organisms or materials that have lived Chemical Rocks- Formed by inorganic processes such as evaporation or precipitation Chemical Rocks- Formed by inorganic processes such as evaporation or precipitation

Clastics Rocks Conglomerate Breccia Conglomerate Breccia rounded pieces angular pieces rounded pieces angular pieces Sandstone Sandstone Mudstone Mudstone Conglomerate Breccia Conglomerate Breccia rounded pieces angular pieces rounded pieces angular pieces Sandstone Sandstone

Organic Rocks Coquina Fossiliferous Limestone Coal Chalk Coquina

Chemical Rocks Limestone Limestone Rock salt

Where do Sedimentary Rocks form? End of or along rivers or deltas, swamps and bogs, oceans, or anywhere sediment is found End of or along rivers or deltas, swamps and bogs, oceans, or anywhere sediment is found Examples: limestone, sandstone, coal Examples: limestone, sandstone, coal

Some Unique Characteristics of Sedimentary Rock Fossils Fossils Ripple Marks Ripple Marks Mud Cracks Mud Cracks Geodes Geodes

How was coal formed?

More about coal Coal is a combustible black or brownish- black sedimentary rock composed mostly of carbon and hydrocarbons. It is the most abundant fossil fuel produced in the United States. Coal is a combustible black or brownish- black sedimentary rock composed mostly of carbon and hydrocarbons. It is the most abundant fossil fuel produced in the United States. Coal Vein

Coal is a nonrenewable energy source because it takes millions of years to create. Coal is a nonrenewable energy source because it takes millions of years to create. The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth was partly covered with swampy forests. The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth was partly covered with swampy forests. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers helped the plant remains turn into what we today call coal. The heat and pressure from the top layers helped the plant remains turn into what we today call coal.

Types of Coal Coal is classified into different types depending on the amounts and types of carbon it contains and on the amount of heat energy it can produce. Coal is classified into different types depending on the amounts and types of carbon it contains and on the amount of heat energy it can produce. The rank of a deposit of coal depends on the pressure and heat acting on the plant debris as it sank deeper and deeper over millions of years. For the most part, the higher ranks of coal contain more heat- producing energy The rank of a deposit of coal depends on the pressure and heat acting on the plant debris as it sank deeper and deeper over millions of years. For the most part, the higher ranks of coal contain more heat- producing energy

Lignite is the lowest rank of coal with the lowest energy content. Lignites tend to be relatively young coal deposits that were not subjected to extreme heat or pressure. Lignite is crumbly and has high moisture content. Lignite is the lowest rank of coal with the lowest energy content. Lignites tend to be relatively young coal deposits that were not subjected to extreme heat or pressure. Lignite is crumbly and has high moisture content.

Bituminous coal contains percent carbon, and has two to three times the heating value of lignite. Bituminous coal was formed under high heat and pressure. Bituminous coal in the United States is between 100 and 300 million years old. It is the most abundant rank of coal found in the U.S., Bituminous coal contains percent carbon, and has two to three times the heating value of lignite. Bituminous coal was formed under high heat and pressure. Bituminous coal in the United States is between 100 and 300 million years old. It is the most abundant rank of coal found in the U.S., accounting for about accounting for about half of U.S. coal half of U.S. coal production. production.

Anthracite contains percent carbon and its heating value is slightly lower than bituminous coal. Anthracite is very rare in the United States. The only anthracite mines in the United States are located in northeastern Pennsylvania. Anthracite contains percent carbon and its heating value is slightly lower than bituminous coal. Anthracite is very rare in the United States. The only anthracite mines in the United States are located in northeastern Pennsylvania. Anthracite Coal is a Metamorphic Rock that is made after Bituminous Coal undergoes heat and pressure

Metamorphic Rocks ROCKS

Metamorphic Rocks Parent igneous and sedimentary rocks are changed into a new form due to heat and pressure Parent igneous and sedimentary rocks are changed into a new form due to heat and pressure Examples: a granite changes to a gneiss; shale changes to slate Examples: a granite changes to a gneiss; shale changes to slate

Metamorphic Rocks Formed from heat and pressure changing the original or parent rock into a completely new rock. The parent rock can be either sedimentary, igneous, or even another metamorphic rock. Formed from heat and pressure changing the original or parent rock into a completely new rock. The parent rock can be either sedimentary, igneous, or even another metamorphic rock. Different types of metamorphism—see notes about each type. Different types of metamorphism—see notes about each type.

Metamorphism can be regional or local Metamorphism can be regional or local Regional – mountain building Regional – mountain building Local (burial) – smaller areas Local (burial) – smaller areas Contact – hot magma melts nearby rocks Contact – hot magma melts nearby rocks Deformational – high pressure areas at faults Deformational – high pressure areas at faults

Local vs. Regional

Metamorphic Rocks Foliated- Parallel alignment of flattened mineral grains and pebbles Foliated- Parallel alignment of flattened mineral grains and pebbles polymineralic polymineralic Unfoliated-Rocks that are not banded and do not break into layers Unfoliated-Rocks that are not banded and do not break into layers monomineralic monomineralic

Foliated Visible banding as minerals layer according to density—heat, pressure and chemical action

Before and After Granite (Igneous Rock) Gneiss (Metamorphic Rock) Parent RockMetamorphic Rock GraniteGneiss BasaltSchist ShaleSlate

Unfoliated Monomineralic—one mineral Since only one mineral present, no banding can occur

2. Nonfoliated – form when existing rock (parent rock) is placed under great heat and pressure and the mineral crystals are not arranged in parallel bands. *Usually due to contact with magma. Examples of Nonfoliated Metamorphic rocks: Parent Rock Metamorphic Rock Sandstone (quartz minerals) Quartzite LimestoneMarble

Rock Cycle – a cycle which shows how one rock type changes into another rock type (it’s a never-ending cycle)

The Rock Cycle

The diagram of the rock cycle shows how the earth's rocks are changed again and again The diagram of the rock cycle shows how the earth's rocks are changed again and again Rock Cycle

Distribution of Rocks in the U.S.

The Rock Cycle and Virginia

The Provinces

The Coastal Plain Rock material consists of sands, silts, and clays Rock material consists of sands, silts, and clays A terraced or stair-step sort of landscape that goes from the west edge to the coast and major rivers A terraced or stair-step sort of landscape that goes from the west edge to the coast and major rivers Large tidal rivers Large tidal rivers The “Fall Line” lies along the western edge The “Fall Line” lies along the western edge

The Piedmont Largest province of Virginia Largest province of Virginia Mainly farmland and horse country Mainly farmland and horse country The Piedmont has gently rolling hills and small valleys The Piedmont has gently rolling hills and small valleys Made up of igneous and metamorphic rocks (slate) Made up of igneous and metamorphic rocks (slate) Oldest rocks are about 1100 million years old Oldest rocks are about 1100 million years old The “Fall Line” lies along the eastern edge The “Fall Line” lies along the eastern edge

The Fall Line The Fall Line is a series of waterfalls and rapids The Fall Line is a series of waterfalls and rapids The Fall Line is formed by these rivers and streams flowing from the older, harder rocks on the western side to the softer rocks on the eastern side. The Fall Line is formed by these rivers and streams flowing from the older, harder rocks on the western side to the softer rocks on the eastern side.

The Valley and Ridge Made up of ridges and valleys Made up of ridges and valleys Rock type is sedimentary— limestone, sandstones and shales Rock type is sedimentary— limestone, sandstones and shales Caves and sinkholes due to the easy erosion of limestone Caves and sinkholes due to the easy erosion of limestone

The Appalachian Plateau Smallest Virginian Province Smallest Virginian Province Plateau is a raised piece of land and is higher than the Valley and Ridge Plateau is a raised piece of land and is higher than the Valley and Ridge Very rich in resources—coal is Virginia’s most economical resource Very rich in resources—coal is Virginia’s most economical resource