Unit 2 Geosphere notes compilation Part 1

Igneous Rocks

formed from the cooling of liquid rock

Igneous rocks are determined by

How fast it cools

Composition of melted rock

Magma

lava found deep underground

Lava

when magma erupts and comes to the surface

Intrusive igneous rocks

formed deep beneath the surface and have been cooling for millions of years. These rocks are characterized by large crystals. Ex. Granite

Extrusive igneous rocks

Forms on the surface of the earth, lava erupts and cools quickly; little to no crystal growth ; Ex. Obsidian, pumice

Coarse Grained

Large crystals, slow \n cooling

Porphyritic

Both large and small crystals, \n slow cooling with different minerals

Fine Grained

Small crystals, fast cooling

Glassy

No crystals, instant cooling

Most common minerals on earth

Silicates

Felsic light

rock made up mostly of silicates \n ○ over 65% silica

Andesitic medium

rock that is half dark/light \n ○ between 55-65% silica

Mafic dark

rock that is rich in Fe and Mg \n ○ Between 45-55% silica

Ultramafic

rocks rich in Fe and Mg \n ○ Under 45% silica

sedimentary rocks

an accumulation of various types of sediments; mostly form underwater ex. limestone, halite

Sediments

Fragments that result from the breaking (weathering) of rocks, minerals, and organic matter. Ex. Gravel, clay, silt, pebbles, sand, mud, shells, dirt;

Clastic

Formed from fragments of other rocks which have been weathered and eroded

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Classified by the size of the sediments (coarse-pebbles or larger, medium-sand sized, or fine-clay or silt sized)

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Examples: Sandstone (sand), shale (silt or clay), conglomerate (round pebbles), and breccia (angular pieces)

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Organic

Formed from the remains or traces of animals and/or plants

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Example: Coal (plants), chalk (animal skeletons), organic limestone (shells-CaCO3

Chemical

Definition: Formed from minerals that were once dissolved in water.

Either the minerals “settle” out of the water (precipitates) or the water evaporates leaving the minerals behind (evaporates)

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Classified by: their mineral composition

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Example: Chemical Limestone (CaCO3), gypsum (CaSO4), halite (NaCl)

types of sedimentary rocks

Clastic, Organic, Chemical

Stratification

i.e. layering; occurs when there is a change in the kind of sediment deposited. ex. Grand Canyon

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Ripple marks

formed from the action of wind or water on sand (seen in sandstone)

Fossils

remains or traces of plants and/or animals

Metamorphic rocks

Rock formed from other rocks (igneous, sedimentary, or metamorphic) as a result of intense heat (from magma) and pressure (plate tectonics) ; forms below the surface of the earth

Contact Metamorphism

occurs when hot magma pushes through existing rock and \n changes the structure and composition of the surrounding rock. The original minerals may form larger crystals.

Regional Metamorphism

occurs when tectonic plates push against each other \n causing heat and pressure that chemically changes the minerals in the rock (most metamorphic is formed this way).

Foliated Metamorphic rock

Pressure flattens the mineral crystals and pushes them into parallel bands. Minerals with different densities separate into different bands ex. Slate, schist, gneiss

Nonfoliated Metamorphic Rock

No visible parallel bands ex. Quartzite, marble

Parent rock

the rock from which a metamorphic rock is formed

Rock cycle

Rock materials are constantly being recycled \n and each rock type can become a different \n type on its journey \n

Energy that drives the rock cycle

Heat

Mechanical

Weathering

The break-up of rock due to exposure to the atmosphere (H2O + gases)

Erosion

removal and transport of earth materials by natural agents (glaciers, water, winds)

Mechanical weathering

rock is broken down into smaller pieces of the same material; No change in the composition; ex. Rock cliff ->pebbles and boulders same as cliff

Abrasion

rocks hitting other rocks

frost action ice wedging

water seeps into cracks in rocks, then \n freezes > expands > melts > refreezes

Wetting and Drying

effective in breaking up rocks containing clay ) Clay swells up \n when wet and shrinks when dry > causing rocks to fall apart

Plant and Animal Action

(mosses, ants, \n earthworms, moles) \n - plant roots grow into cracks \n - wedging rock apart; \n animals dig into the earth

Exfoliation

peeling of rock layers due to gravity (sheet of rock peels away) Happens to granite

Chemical Weathering

Rock’s minerals are changed into different substances; change in composition and appearance; occurs when a chemical reaction takes place between the rock and H2O, CO2, O2, or acid

Hydrolysis

Chemical reaction of water and minerals ex. Feldspar + H20 > Kaolin ( clay)

Oxidation

Chemical reaction of oxygen + minerals ( occurs in rocks with iron) ex. Fe + O2 > FeO2 (iron oxide) Hematite or \n rust

Carbonation

chemical reaction of CO2 (dissolved in water) and minerals> produces carbonic acid and results in a mineral changing

Acids

(plant decay, industrial runoff, and acid rain) acid seeps into rocks and produces cracks > rocks break apart

act together

Mechanical and Chemical

more surface area

faster weathering

Regolith

layer of weathered rock fragments that covers most of the earth’s surface

Bedrock

solid, unweathered rock that lies beneath the regolith

types of bedrock

solid and broken

Soil composition

Air - 25%

Organic Matter - 4%

Minerals -46%

Water- 25%

Soil is made of

a mixture of weathered rock particles and organic material \n (humus) mostly coming from plants ; mostly sand, clay, or silt particles

Clay

smallest particle size (less than .002 mm); weathered from rocks containing feldspar or aluminum.

Silt

Medium particle size (.002 mm - .06 mm); often found around river banks, river beds or lake beds.

Sand

largest particle size (.06 mm – 2 mm); weathered from rocks containing quartz.

Soil Profile

Cross section in which layers ( a.k.a horizons) of soil and bedrock can be seen

A horizon

consists of topsoil (mostly sand and some clay) rich in humus (O horizon) and leached soil deficient in humus and minerals.

B horizon

subsoil reddish brown in color; made mostly of clay; rich in minerals and nutrients

C horizon

deepest layer; consists of broken and solid, unweathered bedrock.

Humid tropical climates

Thick O \n horizon > laterite (acidic soil).

Desert climates

thin soil consisting mostly of regolith

Pedalfur

found in areas E. of Mississippi River that receive more than 65 cm of rain a year; mostly clay, quartz and iron; acidic

Pedocal

found in areas W. of Mississippi River in areas receiving less than 65 cm of rain a year; contains Ca, less acidic, very fertile

ncs main soil type

Cecil ; found above granitic rock ; thick red subsoil

soil erosion factors

* Climate
* Slope Steepness
* Type of Vegetation

Soil conservation combats this

Terracing

Step like ridges are built and arranged \n sideways on a hill. Slows down water erosion.

Contour plowing

Cultivated rows run sideways, rather than up and down. Slows down water erosion.

Strip cropping

Different crops are grown on the same piece of land and rotated the next year. Catches soil eroded from other crop.

Shelter belt

Rows of trees are planted close together to help force wind movement upward, away from the ground.

Slash and Burn

the cutting and burning of plants in forests or woodlands to create fields

Clear Cutting

most or all trees in an area are uniformly cut down

Tilling

Preparing a field by digging, stirring, or overturning soil

Monoculture

growing a single crop or plant species over a wide area and for many consecutive years

Crop Rotation

Growing different crops in succession in the same field Replenish soil nutrients

Cover Crops

– Prevent soil erosion \n – Suppress weeds

Soil Enrichment

Add a layer of manure, mulch the soil, or \n add compost

Integrated Pest Management

\-Solve pest problems while minimizing risks to people and the environment

Mass Movement

\n The movement of rock fragments down an incline as a result of gravity.

Talus

a pile of rocks that accumulate at the base of a slope.

Landslide

Sudden movement of loose rock and soil down a slope of a hill, mountain or cliff. \n –Caused by heavy rainfall, spring thaws, volcanic \n eruptions and earthquakes. \n –ex. Avalanche

Creep

Slow, downhill movement of rock and soil; it will cause fixed objects such as trees, fence posts, light poles in soil to lean downhill. – Usually goes unnoticed until objects begin to lean. – Caused by excess water in the soil, plant roots, burrowing animals, and alternating freezing/thawing.

Slump

A mass of loosened rock and soil moves downhill in one large chunk. \n –Caused by excess water in the soil which causes a \n loss of friction allowing rock to slip downhill

Mudflow

Clay and silt saturated with water flow rapidly \n downhill. \n –Caused by heavy rain. \n –Usually occurs in dry, mountainous regions during \n sudden heavy rainfall. \n –Very dangerous....can wash out roads and destroy \n buildings.

Stabilization

In mountainous areas where mass movement \n is potentially possible steps are needed to \n prevent death and damage to property. \n • Methods include \n –Concrete retaining walls/ retaining bolts \n –Drainage pipes to reroute water \n –Grading the slope \n –Explosives

wind erosion occurs in

* Places where there is little vegetation (plants, trees, grass)
* Places where there is little water (moisture makes the soil heavier🡪 harder to move)
* Ex. Beach and desert

Saltation

Wind causing sand to jump and bounce and move

Deflation

wind removes topsoil, **lowers the land** and leaves rock fragments that are too large to be lifted.  Common in deserts.

* Example: Dust Bowl

Abrasion

Rocks get worn down and smoothed mostly by blowing sand.

Dunes

Sand gets deposited by the wind; mounds of sand blown by the wind. Common in deserts, on beaches and on the shores of large lakes.

Glaciers

Very large moving masses of ice; form near Earth’s poles and in mountains at high elevations; snow in these areas is compacted and recrystalized into ice

Valley Glaciers

these glaciers form in valleys and in mountainous areas; They flow down the valleys like a thick  liquid; will carve and widen a valley 

Continental Glaciers

Glaciers that cover a continent-sized area ; form in very cold, polar regions. (Ex. Antartica, Greenland)

Advancing Glaciers

These glaciers are growing

Retreating Glaciers

These glaciers are shrinking

Icebergs

Come off of glaciers in a process called calving

Till

Sediment left behind as a glacier moves and melts

Moraine

An accumulation of sediment on the sides of a glacier

Kettle lake

formed when a large piece of ice breaks off and is left to melt.

Meltwater stream

a stream formed from melted glacier water

Outwash plain

meltwater streams can carry sediment down the glacier and then deposit them on dry land.