The Water Cycle Water turns into steam by evaporation and transpiration ground back to the oceans, lakes and plants. It then condenses in the lower atmosphere & eventually precipitates as rain, snow, etc. The water then flows over the ground as rivers and under the (oceans and lakes) (evaporation directly from plant leaves). 1

When air warms up, more water evaporates or transpires. This makes warm, humid air and when you warm a fluid, the warm, humid air will expand, become less dense and rise. As the air rises, it cools and then it will become more dense and it will eventually sink. 2

Weathering  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 3

 Meanders & Oxbow lakes are formed by surface water erosion on level or gently sloping land 4

 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 5

Erosion - 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 6

 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 7

8 Sea stacks

9 Upwelling Longshore drift

 Deflation  Abrasion 10

 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. 11

Portage Glacier in Alaska - probably the most visited glacier in AK. 12

Moraine 13 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 Effects Aquifer – permeable rock that is saturated with water Landslide – 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 H 2 0 Upwelling – ocean current rising cold, deep H 2 0 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 14

Weathering Terms Chemical 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 15

Other Important Terms Radioactive 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 16

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,

18 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

Glacial Horn in Nepal 19

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21 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 22 Geologists use the law of superposition to determine the relative age of rocks. In sedimentary rock, older rock is in a deeper level Index 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 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 mg 2. 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 years 3. How long will it take for 80.0 mg of Rb-87 to decay into 10.0 mg? T ½ for Rb-87 is 48.8 billion years. 10/80 = 1/8 = 1/2 3. The exponent tells 3 half lives so 3 x 48.8 billion years = billion years !!!

Main Divisions of Earth’s History (Pg 734-5) 24 Precambrian Paleozoic Mesozoic: Contains periods: Triassic, Jurassic, Cretaceous Cenozoic The first land plants and animals appear in the fossil record during the Paleozoic Period. Preca mbria n Camb rian Ordov ician Siluria n Devon ian Carbo nifero us Permi an Triassi c Jurassi c Cretac eous Tertia ry Quate rnary PaleozoicMesozoicCenozoic Millions of years ago: