Chapter 6.1

Formation of Sedimentary Rocks

Vocabulary• Texture- the size, shape, and crystal size • Sediment- Pieces of solid material that have

been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation.

• Lithification- physical and chemical process that transform sediments into sedimentary rocks.

Vocabulary Cont.• Cementation-when mineral growth cements

sediment grains together into rock.• Cross-bedding- bedding in which the particle

sizes become progressively heavier and coarser towards the bottom layers.

• Graded bedding- bedding formed when inclined layers of sediment move forward across horizontal surface.

• Bedding- horizontal layering of sedimentary rocks.

Weathering Weathering

Produces clastic sediment

Physical Processes

Minerals in rock are

chemically unchanged.

Rock fragments break off.

Occurs when Earth’s crust is exposed

Chemical Processes

Minerals in rocks are

chemically changed.

Occurs through

Erosion and Transport

Wind Moving Water

Gravity Glaciers

Process of Lithification

• Lithification begins when the weight of overlaying sediments forces sediment grains closer together. Water in pressed out. The grains are then compacted together. Sediments that are buried will experience high temperatures and will have cementation.

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Section 6.2 Vocab

Clastic: sediments having particles ranging in size from boulders to microscopic particles, which often have worn surfaces and rounded corners.Clastic Sedimentary Rock: sedimentary rocks formed from deposits of loose sedimentsPorosity: the percentage of open spaces between grains in a rockEvaporite: chemical sedimentary rocks that form as a result of crystal grains precipitating out of a supersaturated body of waterReservoir: a subsurface area of rock that has enough porosity to allow for the accumulation of oil, natural gas, or water

Clastic sedimentary rocks

Coarse-grainedType of fragments: gravel sizeTypes of rock formed: conglomerate, brecciaFormed by: high-energy flows of water

Medium GrainedType of fragments: sandType of rock formed: sandstoneFormed by: stream and river channels, beaches, deserts

Fine-grainedType of fragments: silt and mudType of Rock formed: siltstone, shale

Medium-grained clasticsPorosities as high as 30-40%-When pore spaces connected it allows for water to move through sandstoneCan hold reservoirs of oil, natural gas, and groundwater

Fine-grained clasticsVery low porosityForm barrier to the movement of groundwater and oil

Chemical Sedimentary Rocks

Chemical Sedimentary Rocks

Sequence

___ Thick layers of evaporites can accumulate as evaporation removes freshwater.___ Water evaporates and leaves behind dissolved minerals.___ Minerals are dissolved and carried into lakes and oceans by chemical weathering.___ Layers of chemical sedimentary rocks called evaporites form.___ The concentration of minerals reaches the saturation point.___ Crystal grains precipitate out of the solution and settle on the bottom.

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Biochemical Sedimentary RocksWhat forms themThe remains of the once-living animals and plants

Where they formShallow-water environments Swamps and coastal areas

How limestone formsOrganisms use calcium carbonate in seawater to make their shells. Calcium carbonate precipitates out of the water and crystallizes between the grains of calcium sediment during lithification.

How Coal formsThick layers of vegetation accumulate. The layers are buried and compressed and are lithified into coal.

Importance of Sedimentary Rocks

Provide Information

about

SedimentaryRocks

ProvideResources

PastAnimals and

plantsBedrock

AncientRivers, lakes,

And shorelines

Uranium PhosphateAnd iron

Oil, naturalGas, and coal

Buildingmaterials

Real-World ConnectionA company want to drill a new oil well. They know that a layer of oil containing shale is located beneath a thick layer of siltstone. Describe challenges the company might face.

The siltstone has low porosity, so the oil will not flow though it. The company would have to drill though the siltstone to reach the oil-containing shale. If the layer of siltstone is too thick, the company might not be able to drill deep enough to reach the oil.

6.3 Metamorphic Rocks

Intrusive- Igneous rocks that cool slowly beneath Earth’s surface

Regional Metamorphism- Belts of metamorphic rock covering large areasContact Metamorphism- Metamorphism that occurs when molten rocks come in contact with solid rocks.Hydrothermal Metamorphism- Metamorphism caused when very hot water reacts with rocks and alters its chemistry and mineralogy.Foliated- Metamorphic rocks containing wavy layers and bands of minerals.Nonfoliated- Metamorphic rocks composed of minerals with blocky shapes.Rock Cycle- The continuous cycle of changing and remaking rocks.

Causes of Metamorphism

Conditions necessary for metamorphism

High Pressure

1. Materials being buried alive 2. Igneous intrusion

Low Pressure

Can be caused by

1. Weight of the rocks above

2. Compressive forces during mountain building

Types of Metamorphism

I. Regional Metamorphism A. Occurs when high temperatures and pressure affect large regions of Earth’s crust. B. Geologists can divide metamorphic rock belts into zones based on the mineral groups found in the rocks.II. Contact Metamorphism A. Occurs when magma comes in contact with solid rock. B. Can result in zones of different mineral surrounding an intrusion.III. Hydrothermal Metamorphism A. Occurs when very hot water reacts with rock and changes its chemistry and mineralogy. B. Can result in dissolved minerals, break down of minerals, and deposits of new minerals.

Metamorphic TextureTexture Shape of

crystalsHow formed Examples

Foliated Flat, needlelike

High pressure during metamorphism

Schist, gneiss

Nonfoliated blocky No pressure during metamorphism

Quartzite, marble

Porphyroblast Very large Reorganization of atoms during metamorphism

garnet

Mineral Changes

Like in fractional crystallization. Minerals in solid rock are stable at certain temperatures and pressures. During metamorphism. The minerals in rock change into new minerals. The new minerals are stable under the new temperatures and pressure conditions. These kinds of changes are called solid- state alterations.

Compare mineral changes in metamorphism to changes in fractional crystallization. Name the process of mineral change in metamorphism.

Composition Changes Hot fluid movie in and out of rock during metamorphism. This can change the original composition of the rock. Chemical changes often happen during contact metamorphism near igneous intrusions. Hydrothermal fluids move into the surrounding rocks and change their mineralogy, texture and chemistry.

Synthesize

Rocks are constantly changing from one type through internal and external processes. A rock’s age tells when it took its present form.

A geologist says that a certain rock us 500 million years old. Tell if this can be true, and why or why not.

Other Metamorphic is Latin of “Changed form” James Hutton proposed the rock cycle in the

1700’s