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The Water CycleWater turns into steam by evaporation

and transpiration

ground back to the oceans, lakes and plants.

It then condenses in the lower atmosphere & eventually precipitates asrain, snow, etc.The water then flows over the ground as rivers and under the

(oceans and lakes)(evaporation directly from plant leaves).

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When air warms up, more water evaporates or transpires. This makes warm, humid air and when you warm a fluid, the warm, humid air willexpand, become less dense and rise.

As the air rises, it cools and then it will becomemore dense and it will eventually sink.

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Weathering and ErosionWeathering Physical - breaks rock into smaller

pieces without changing chemical composition  Ice

When water freezes to form ice, the water expands. This expansion acts like a wedge and opens the gaps the water has entered

Plants Plant roots grow into the small

crack in rocks. Once there they provide a strong force that gradually pries the rock apart through the cracks

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Erosion by Water

Meanders & Oxbow lakes are formed by surface water erosion on level or gently sloping land

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Chemical – process in which rock is broken down by chemical reactions. Water is an effective solvent that dissolves the

minerals in rock, changing them over time Rusting of minerals rich in iron involves

oxidation acid rain can dissolve minerals (water and

carbon dioxide combine to form carbonic acid) The carbonic acid in the rain water can dissolve

minerals causing underground caves 1990 the acid rain act was added to the 1970

clean air act that required power plants and factories to reduce the release of sulfur dioxide

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ErosionErosion - process by which rock and /or the products of

weathering are removed.

Water – running water erodes land Moving water scrapes the earth and carries sediment

away to new places. Faster water carries heavier sediments while slower

water cannot, resulting in the releasing of these sediments

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Other Water Terms

Longshore drift moves sand along the shore.

A sea stack is formed by wave erosion.

Density differences in ocean water cause deep currents.

An upwelling brings cold water from deep ocean to the surface

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Sea stacks

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Upwelling

Longshore drift

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Wind erodes land by

Deflation Abrasion

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Glaciers – Constantly moving masses of ice exert tremendous force on surrounding forces on rock. Can carry huge amounts of sediment As the glaciers move

they create U-shaped valleys as they cut across the landscape

As the glacier melts it will deposit its sediment to create a new landforms.

Portage Glacier in Alaska - probably the most visited glacier in AK.

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Moraine

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A mound of sediment at the downhill end and sides of a glacier

Medial moraine visible as a dark line along the centre of the glacier. Wide lateral moraines can be seen on either side.

Water – Terms and EffectsAquifer – permeable rock

that is saturated with waterLandslide – rock and soil

moving down a slope rapidly

Creep – fences curving down a hillside

Delta – soil deposited when river flows into an ocean

Deep ocean currents – result of density differences in H20

Upwelling – ocean current rising cold, deep H20

Longshore Drift – process that moves sand along shore

Frost wedging – water frozen is cracks pushed out soil and rock

Most of Earth’s fresh water is found in groundwater.

A stream’s ability to erode is a result of its speed

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Weathering TermsChemical Weathering

Agents:Rainwater, oxidation,

carbonic acid

Chemical weathering – evident most on limestone in hot, rainy area

Cave & sinkhole formation – by chem weathering

Caves can be formed by groundwater formation

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Other Important TermsRadioactive Isotopes

– used to more precisely determine the age of rocks

Rad. Isotopes, Index fossils, relative dating – used to determine age of sedimentary rocks in different locations

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Alluvial Fan

• Alluvial Fan• Credit: USGS EROS Data Center; NASA • A vast alluvial fan blossoms across the desolate landscape

between the Kunlun and Altun Mountains that form the southern border of the Taklimakan Desert in China's XinJiang Province. The river appears electric blue as it runs out of the mountains at the bottom right corner of the scene and then fans out into scores of intricate, braided channels that disappear into the desert. Dry channels - the river's former paths - appear as silvery etchings at lower right. This scene was acquired by the ASTER instrument on NASA's Terra satellite on May 2, 2002

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Alluvial FanCredit: USGS EROS Data Center; NASA A vast alluvial fan blossoms across the desolate landscape between the Kunlun and Altun Mountains that form the southern border of the Taklimakan Desert in China's XinJiang Province. The river appears electric blue as it runs out of the mountains at the bottom right corner of the scene and then fans out into scores of intricate, braided channels that disappear into the desert. Dry channels - the river's former paths - appear as silvery etchings at lower right. This scene was acquired by the ASTER instrument on NASA's Terra satellite on May 2, 2002

Glacial Horn in Nepal

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Sinkholes are depressions or holes in the land surface that occur throughout west central Florida. They can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone.

Hydrologic conditions, including lack of rainfall, lowered water levels, or, conversely, excessive rainfall in a short period of time, can all contribute to sinkhole development. More facts about sinkholes can be found in the District’s

Earth’s History

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Geologists use the law of superposition to determine the relative age of rocks.In sedimentary rock, older rock is in a

deeper levelIndex fossils that lived during a well-

defined period of time are used to determine relative age, also.

Radioactive dating is used to determine the absolute ages of rocks.Half life is the time it takes for half of a

radioactive substance to change into something else. Seeing how many half lives have passed, can be used to tell how much time has passed; and how old something is.

Exploring Radioactive Dating

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1. A fossil contains 40.0 milligrams of U-238, which has a half life of 4.5 billion years. How much U-238 will remain after two half lives?

40.0 mg divided by 2 divided by 2 = 40/4 =10.0 mg2. How long will it take for 50.0 mg of Th-232 in a rock

to decay to 25.0 mg? One half life for Th-232 is 14.0 billion years.

25/50 = s½ so, 1 half life or 14.0 billion years3. How long will it take for 80.0 mg of Rb-87 to

decay into 10.0 mg? T½ for Rb-87 is 48.8 billion years.

10/80 = 1/8 = 1/23 . The exponent tells 3 half lives so 3 x 48.8 billion years = 146.4 billion years !!!

Main Divisions of Earth’s History(Pg 734-5)

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PrecambrianPaleozoicMesozoic: Contains periods: Triassic,

Jurassic, CretaceousCenozoic

The first land plants and animals appear in the fossil record during the Paleozoic Period.

Precambrian

Cambrian

Ordovician

Silurian

Devonian

Carboniferous

Permian

Triassic

Jurassic

Cretaceous

Tertiary

Quaternary

Paleozoic Mesozoic Cenozoic

Millions of years ago:4600 544 505 440 410 360 286 248 213 145 65 18 0