Weathering, Sedimentary and Metamorphic Rocks

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The Rock Cycle

the processes by which rock is formed, modified, transported, decomposed, and reformed as a result of the Earth's internal and external processes.

Weathering

The chemical and physical breakdown of rocks exposed to air, moisture, and organic matter.

Regolith

The loose layer of broken rock and mineral fragments on the Earth's surface.

Mechanical Weathering

rock is physically broken up, but there is no change in the mineral content or chemical composition.

Chemical Weathering

the decomposition of rocks and minerals as a result of chemical and biochemical reactions.

Hydrolysis

A type of chemical weathering that is leads to the change in silicate minerals to salt and clays.

Oxidation

A type of chemical weathering that alters iron and manganese by exposure to oxygen.

Quartz

is very resistant to weathering and does not dissolve quickly or have an ion exchange.

Rock Structure

If there are many cracks or joints in a rock, water can get in and weather rocks more quickly through its

Soil

The uppermost part of the regolith, the part that supports rooted plant life.

Humus

Partially decayed organic matter.

Soil Horizons

A succession of zones within a soil profile with distinct physical, chemical, and biological characteristics.

Soil Profiles

The sequence of soil horizons down to the bedrock.

Erosion

The transportation of regolith from one place to another and abrasion of the Earth's surface by materials being transported.

Mass Wasting

Downslope movement of regolith and/or bedrock masses due to the pull of gravity.

Saltation

Sediments moving by bouncing off of each other.

Erosion by water

Sediments carried in the suspended load(small) and the bed load(large).

Erosion by wind

Wind cannot move sediments that are as large as water can carry. Sorts sediment better than water.

Erosion by ice

sediment carried by glaciers and carves groves in the bedrock.

Falls

A sudden vertical drop of rock fragments and debris.

Slide

Rapid displacement of mass movement down a planar slope.

Slump

a rotational movement of rock.

Flow

Any mass wasting process that involves flowing of mass regolith.

Creep

Imperceptibly slow downslope flow of regolith.

Frost Heaving

Uplift of surface rock and regolith as a result of the freezing of subsurface water to form ice.

Sedimentary Rocks

produced from weathering products of pre-existing rocks or accumulated biological matter.

Detrital

rocks produced from rock fragments.

Chemical

rocks produced by precipitation of dissolved ions in water.

Organic

rocks produced by accumulation of biological debris, such as swamps or bogs.

Sediment

loose, solid particles originating from weathering and erosion of pre-existing rocks.

Transportation

Movement of sediment away from its source. Typically by water, wind, or ice.

Deposition

Settling and coming to rest of transported material.

Preservation

Sediment must be preserved, as by burial with additional sediments, in order to become and sedimentary rock.

Lithification

The processes of changing sediment to sedimentary rock.

Clastic Rocks

Classified by grain size and shape. Ex. Breccia, Conglomerate, Sandstone, and Shale.

Conglomerate

Round grains

Breccia

Angular grains

Sandstone

sand-sized grains

Shale

smaller than sand-sized grains

Evaporates

Chemical sediments that form when water evaporates.

Precipitates

Iron-rich siliceous sediments precipitated out of anoxic sea water more than 18 billion years ago.

Biogenic rocks

Limestones, Chert, Peat, and Coal

Stream Sediment

Carry a lot of sediments in every size of clast. Deposits can be well to poorly sorted, to graded beds.

Lake Sediment

Generally well-sorted sediments or graded beds in deltas that form when streams flow into a lake.

Glacial Sediment

generally poorly-sorted and angular.

Eolian Sediments

Wind blown sediments. Best sorted sediments because only smallest grains are carried by normal winds.

Metamorphism

The mineralogical, chemical, and structural adjustments of solid rocks to physical and chemical conditions at depths below the region of sedimentation and diagenesis.

Foliation

the alignment of minerals in metamorphic rocks.

Slaty cleavage

The quality that causes low grade metamorphic rocks to part or split along a plain.

Schistocity

When the oriented mica grains are large enough to be seen with the naked eye.

Effects of Temperature

As temp increases the minerals that grow are different.

Contact Metamorphism

occurs when rocks are heated and chemically changed by the intrusion of a body of hot magma.

Shock Metamorphism

occurs in a shock such as an asteroid.

Burial Metamorphism

sedimentary rocks that are deeply buried (>10 km) in trenches are altered.

Regional Metamorphism

of an extensive area of the crust as a result of the stresses and high temps associated with plate convergence, collision, and subduction.

Index Minerals

minerals that form at specific pressures and temperatures.

Isograds

lines on maps of occurence of index mineral assemblages.

Foliated Rocks

Slate, Phyllite, Schist and Gneiss

Slightly Foliated

Amphibolite, Granulite, Blueschist, Eclogite

Non-foliated

Marble and Quartzite

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