(Alfred Wegener 1915)
PANGEA- a large landmass containing all of the continents. Which eventually into two landmasses.
Laurasia- North America, Europe, Asia
Gondwanaland- EVIDENCE
continents seem to fit together
fossils of individual species can be found on many different continents which are not lose together. (ex.lystrosaurus was located in Antarctica, south America, Africa, India)
Deposits of certain rock and mineral types correlate among continents.
Appalachian mountains found in northeast of u.s are similar in age and structure as mountains, in Greenland and Scandinavia. STRUCTURE OF THE EARTH
Pressure and temperature increase as you move toward the center of the earth.
CRUST- the outermost layer of the earth.
continental crust- composed mainly of granite, low in density.
oceanic crust- composed mainly of basalt, high in density.
lithosphere- crust and uppermost solid part of the mantle.
asthenosphere- underlies the lithosphere, composed of partially molten rock.
moho- the boundary between the crust and the mantle.
mantle- the layer of molten rock extending from the crust downward 2850 km.
outer core- between mantle and inner core, composed of iron and nickel.
inner core- solid iron and nickel located at the center of the earth. PLATE TECTONICS
http://geology.com/nsta/plate-tectonics-cover.gif
plate tectonics is the study of the formation and movement of plates.
plates are composed of lithosphere (continental=thick, oceanic= thin) 12 major and several minor plates. EARTHQUAKES
an earthquake is a shaking of earth's crust cause by the release of energy. reasons why they occur:
eruption of a volcano
the collapse of a cavern
the impact of a meteor
sudden movement along a plate boundary cause by the release of stress. DEPTH OF EARTHQUAKES *
focus- the point on a fault plane at which the first movement occurs.
epicenter- the point on earths surface directly above the focus. EARTHQUAKE WAVES *
three basic kinds of waves
primary (P)waves- back and forth wave motion; can travel through any material; fastest.
secondary waves(S)- side to side wave motion; can travel through solids but not through liquids or gases.
surface waves(L)- form when p+s waves combine. form when p + s waves reach the surface which move slowly like ripples on a pond:slowest. LOCATING A EARTHQUAKE *
seismograph- the instrument that detects and records earthquake waves.
seismogram- the sheet which displays the zig-zag trace if earthquake waves.
*P-Waves always arrive before S-Waves*
P and S wave arrival time difference can then be used to determine the distance from the recording station to the epicenter.
LOCATING AN EPICENTER
Triangulation- we then use the epicenter distance's from at least 3 recording stations to locate the epicenter.
You need to next measure the distance to scale and drawing a circle from each station. Once 3 circles are drawn they will intersect at one common point. This location is the epicenter.
SHADOW ZONE*
The shadow zone is a wide belt around earth on the side opposite the focus of the earth quake. Seismic stations receive neither P nor S waves.
The cause of the shadow zone is the Earth's outer core.
S-waves can not travel through the liquid outer core. While P waves are refracted (bent) in a smooth arc back to the surface.
-Magma- molten rock underground.
-Felsic- magmas with relatively high silica are thick, light colored, and slow moving.
-Mafic- relatively low silica content, thinner, darker, and flow more easily.
-Magma contains dissolved gases that are given off as the magma erupts. The most important of these gases are water vapor, carbon dioxide, and sulfur.
-Magmas containing large amounts of dissolved gases tend to produce more explosive eruptions.
-Lava- molten rock that has reached the surface.
-Felsic Lava- thick and stiff called AA lava. Produce explosive eruptions.
-Mafic lava- thin and fluid called pahoehoe lava. Lave pours out and smoothly (less explosive)
Lava Fragments
Tephra- solid fragments of lava produced from explosive eruptions.
Kinds of Eruptions
Rift Eruptions- Occur at long, narrow fractures in the crust such as mid-ocean spreading centers.
When lava flows out smoothly and fluidly it forms a volcanic mountain with a broad base and gently sloping sides called a shield zone.
Subduction boundary eruptions are the result of thick magma that forms at Subduction boundaries.
These eruptions are more explosive due to the large amounts of gases in the magma.
Forms a cinder cone with very steep sides.
Hot Spots
Hot spots are areas of volcanic activity in the middle of the lithosphere plates.
Similar to rift eruptions. Smooth flowing lava and shield cones.
The hot spot stays in the same location as the lithosphere plate about it moves.
Root Wedging (plant action)- Tiny roots grow into cracks in the rock and then as the root grows the rock splits.
Exfoliation- when large masses of rock, mainly igneous, are lifted up to the surface the relief of overlying pressure causes the rock to expand. Upward expansion leads to curved breaks which may peel off in layers
Chemical Weathering- The breakdown of rock through a change in mineral or chemical composition.
Oxidation- The chemical reaction of oxygen with other substances. Iron is most easily attacked resulting in rust (iron oxides)
Carbonic Acid- When carbon dioxide dissolves many common minerals.
Minerals Resistance to Weathering- Different minerals and rocks have different physical and chemical properties which
allow them to weather at different rates.
• Quartz- almost unchanged by chemical weathering. It is hard and does not have cleavage so it also resists mechanical weathering.
• Feldspar, Mica, Calcite, and Gypsum- affected by both types of weathering and will break down into clay with calcite and gypsum dissolving and being carried off in solution.
Sedimentary Rocks-
• Shale- is the least resistant to mechanical weathering
• Sandstone- is the most resistant to mechanical weathering
- The type of cement which holds the sandstone together determines how resistance the rock is Calcite- low resistance and Silica- high resistance.
-Rocks which contain the mineral calcite, such as Limestone or Marble are somewhat resistant to mechanical weathering but is the least resistance to chemical weathering.
Factors Affecting Rate of Weathering!
Exposure- the closer to the surface of the earth, the faster it will weather.
- Rate and type of weathering depends on exposure of rocks to air, water and the action of living things.
Surface Area- The greater surface area exposed to the weathering the faster the rate of weathering.
Two samples of the same material having the same mass can have different surface areas. If one sample is a large piece of marble with a mass of 50g, and the other is 50g of many small pieces of marble. The smaller size pieces will
have the greater surface area.
Climate effect on Weathering.
Chemical weathering- is usually greater in warm, moist climates.
Physical Weathering- usually greater in moist areas with temperature variations (cold and warm)
Soils- soil is made of loose, weathered rock and organic material in which plants with root can grow. The rock material is composed sand, silt, and clay.
Parent material- the material from which a soil is formed.
Residual Soil- soil that has the bedrock beneath the soil as a parent material
Transported Soil- soild formed from deposits left by winds, rivers, and glaciers.
A-Horizaon (Top Soil)- darkest color due to organic material.
B-Horizaon (Subsoil)- 1) clay is washed to the subsoil
2) May contain soluble minerals, such as calcium and magnesium carbonates
3) color is usually red- brown from iron oxides that form above and wash down
C-Horizon- Made of slightly weathered parent material (rock fragments)
A-horizon Topsoil
Darkest color due to organic material
B-Horizon Subsoil
1) Clay is washed to the subsoil
2) May contain soluble minerals, such as calcium and magnesium carbonates
3) Color is usually red-brown from iron oxides that form above and wash down
C-Horizon
Made slightly weathered parent material (rock fragments)
UN-WEATHERED BEDROCKS
Climate
Tropic soils from in areas with high temperatures and heave rainfall. A thick infertile soil profile is results of heavy rain
Grassland soils from areas with enough rainfall for the heavy grass, but not trees/ About 1 meter thick and fertile
Forest soils form in humid regions with cool seasons. Soil profile is less then 1 meter thick with the developed A, B, and C Horizon
Desert soild form in very dry climates. Soil profile is a few centimeters
Weathering And Erosion
MASS MOVEMENTS
Movements of loose earth material down a slope. Gravity is an aid in weathering and erosion. Steep slopes weather to gentle slopes. Creep- slow, imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to lean downhill.
Water in the soil is what adds the weight. Mudflow- the rapid movement of a water saturated mass of soil.
As the earth on a hill moves from under the tree, the tree continues to grow up towards the light. Slump- occurs when a section of land moves downhill as a while because of a plane of weakness in the underlying soil. Landslide- sudden movement of a mass of bedrock or loose rock down the slope of a hill or mountain. (Avalanche- snow, ice, rock, and soil.) Talus- is a pile of rock fragments at the base of a cliff. Wind Erosion
Wing transports materials by causing their particles to move in different ways. Suspension- a method of transport by which strong winds cause small particles to stay airborne for long distances. Saltation- causes a bouncing of motion of larger particles. Saltation accounts for most sand transport by wind.
Wind erosion is greatest in arid climates (low precipitation) with little vegetation. (Deserts and seashores) Abrasion is a process of erosions found in wind, water, and ice. It occurs when particles such as sand rub up against the surface of rocks or other materials.
Ventifacts are rocks shaped by windblown sediments. Wind deposition occurs in areas where wind velocity decreases.
Dunes are piles of windblown sand that have a gentle side and a steep side.
The gentler slope occurs when the side of which the wind is blowing (windward side). The steeper lope occurs on the side protected from the wind (leeward side.)
Loess- thick deposits of fine lightweight particles (Silt, Clay) that are carried by the wind in great quantities of long distances, they are some of the most fertile soils. GLACIERS
http://www.tertium.co.uk/katie/glacier_5541.jpg
Louis Agissiz is known for the idea that glaciers once covered many parts of the world.
FORMATION OF A GLACIER
Glaciers are accumulations of ice large enough to survive summer melt- forms from snow under pressure, which turns to ice.
Snow line- the lowest level that permanent snows reach in summer.
Highest near the equator.
Firn is granular ice material formed in snow fields from freshly fallen snow become compressed and recrystallizing.
The lower layers become ice and begin flowing downward or outward because of overlying pressure.
Alpine Glaciers (valley glaciers)
Occur in mountain regions above the snow line
Flow downhill and carve out U-shaped valleys.
Continental Glaciers
A glacier that spreads over a wide geographic area. Form in polar areas where the snowline is close to sea level and wide area is above the snow line. (responsible for much of the landscape in NY.)
20,000 years ago, a huge ice sheet, originated in Canada, covered New York State.
The overlying weight of snow and ice causes grains of ice to partially melt and refreeze. As this happens ice grains slip past each other and move downhill.
Glaciers move more rapidly at the surface than at the base and faster at the center than at the sides. Friction with the valley walls slow the flow.
Flows at a slow rate of a few CM to several meters per day.
Crevasses are cracks across the width of the glacier that form when glaciers move over steep slopes.
Ice front is the end of a glacier.
The ice front is the STATIONARY as long as the rate of movement and melting are equal.
A glacier RECEDS when it melts faster than normal.
A glacier ADVANCES when the rate of movement is greater then the rate at which it melts.
Pieces of rock are picked up as glaciers move and then are dragged along the bedrock and/or valley wall.
Fine sand acts as sandpaper and POLISH the bedrock.
Larger sediments leave long parallel scratches called STRIATIONS.
STRIATIONS:
Here are a few depositional features of glaciers:
Moraine is a glacial deposit of unsorted tock material.
Ground moraine- carried along the bottom
Lateral Moraine- long lines of rock pieces along the valley sides.
Medial Moraine- when two glaciers come together and there lateral moraines join together.
Cirque- a steep-walled semicircular basin in a mountain; may contain a lake.
Arete- a sharp narrow ridge found in rugged mountains.
Horn- a steep mountain peak caused by several glaciers carving different sides of the same mountain
Col- a break in an arete (mountain pass)
Truncated spur-occurs when the action of a glacier does not follow the original course of the river that wound round interlocking spurs.
Tarn- a small lake at the base of a cirque.
Hanging valley- a tributary valley that joins a main valley where the latter has been deepened, usually by glacial erosion.
Crevasse- a deep fissure.
Roches Moutonees- (resting sheep) an outcrop of bedrock which has become elongated. Sculpted by a glacier one side is smooth and the other is left rough.
Striations- a series of ridges, furrows or linear marks on a rock or other object that show which way the glacier was moving.
Drift- A load of rock material transported and deposited by a glacier. Till- unstratified soil deposited by a glacier; consists of sand and clay and gravel and boulders mixed together.
Moraine- accumulated earth and stones deposited by a glacier.
a) lateral- forms along side of a glacier
b) medial- merging lateral moraines of two glaciers form a moraine in the middle of the glacier.
c) ground- a melting glacier deposits till in a thin layer over a broad area.
d) recessional- deposits of till that form at the end of a glacier as it retreats.
e) terminal- the end moraine found at the farthest advance of a glacier.
outwash plain- A broad, outspread flat or gently sloping alluvial deposit of outwashin front of or beyond the terminal moraine of a glacier.
kame- an irregularly shaped hill or mound composed of sand, gravel and till.
kettle- Bowl-shaped lakes created by large ice blocks, which formed depressions in Earth's surface.
drumlin- a mound of glacial drift.
rock flour- consists of clay-sized particles of rock, generated by glacial erosion or by artificial grinding.
erratics- Boulders carried long distances by the glaciers and deposited when the glacier melted.
esker- a long winding ridge of post glacial gravel and other sediment; deposited by melt water from glaciers or ice sheets.
Erosion- is the process by which earth materials are moved by natural agents like water, wind and ice.
Running Water
Running Water is the most effective agent of erosion.
The SUN is where running water gets its energy.
Rocks are weathered both Chemically and Physically by running water.
PHYSICAL ABRASION is the term given to the use of sand, pebbles, and even boulders are cutting tools to grind away at the stream bed. During this process the "tools" themselves wear down. CHEMICAL The water dissolves soluble minerals.
Rivers carry rock materials in three ways.
Solution- This is material that is dissolved from the bedrock. Most commonly found in solution are compounds of calcium and magnesium.
Suspension- When small rock particles, such as clay silt and fine sand, are kept from sinking by the turbulence of the stream. This gives the water a muddy look.
Bed Load- sand, pebbles, and some boulders, which most along the stream bed.
CARRYING POWER
Carrying Power is indicated by both the total amount of sediment in a stream and by the side of the particles being moved.
The stream discharge and speed will determine the carrying power of the stream.
Discharge- is the volume of water flowing past a given point at a given time.
Speed- is generally determined by the steepness, or gradient, of its bed.
A stream moving at high speed with a high discharge can carry much larger sediments then a slow moving stream. Example: Spring time snow melting and excessive rain.
THE RIVER VALLEY
Rivers tend to have a V-Shape valley because they tend to flow at high speeds and dig into the stream bed. BASE LEVEL- is the lowest level a river can cut into its bed.
To form a permanent stream rain water must flow down a slope and dig deep enough to cut into the water table. This wearing away of the land to form a stream valley is called head-ward erosion.
A divide is an area of high land that seperates one river valley from another.
On either side of a divide a river system may form. Watershed- is all of the land that drains into the river either directly or through its tributaries.
WATERFALLS ^ Water flowing over a steep cliff will result in a waterfall. Waterfalls are not permanent structures. Undermining- is the erosional process occurring at the base of a waterfall. Here water carrying sediment plunges down and back into the stream ed and cliff below. This causes the rocks at the top of the falls to overhang. Over time this overhang will collapse and the stream will move back towards its source.
RIVER DEPOSITION
Deposition occurs when a strean either decreases in speed or discharge.
Generally the speed decreases when its slope decreases or its bed widens. The greatest loss of speed occurs when a river empties into a quiet body of water.
A decrease in discharge would occur if a river traveled through an area with low precipitation.
The Hudson River is an example.
As rivers begin to decrease their slope they move slower and will begin to move side to side.
As the valley wall on either side is eroded the valley floor is widened.
A Flood Plain is the widened valley floor area which will accumulate water during times of excess rain when the rover floods.
EROSION AND DEPOSITION IN A RIVER
Meanders are broad curves in tge river (each bend or turn)
Erosion is greatest on the outside of a meander where water is flowing the fastest. (cut bank)
Deposition is greater on the inside of the meander where the water flows slower. (fill bank)
Oxbow Lake- Meanders can only become so large before they break through into another meander. The river then deposits mud and silt along the end of the abandoned meander. The now separated meander becomes a lake.
Running water deposits well-sorted particles
Vertical Sorting- When sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top.
Horizontal Sorting- When rivers empty their sediments into quiet bodies of water. Particles are sorted by size with larger particles being found closer to the shore and smaller particles being carried out into the body of water to be deposited.
http://www.mrsciguy.com/sciimages/horizontal.jpg
Delta- a fan shaped deposit of sediment at the mouth of a river.
Theory of Continental Drift
(Alfred Wegener 1915)PANGEA- a large landmass containing all of the continents. Which eventually into two landmasses.
Laurasia- North America, Europe, Asia
Gondwanaland-
EVIDENCE
continents seem to fit together
fossils of individual species can be found on many different continents which are not lose together. (ex.lystrosaurus was located in Antarctica, south America, Africa, India)
Deposits of certain rock and mineral types correlate among continents.
Appalachian mountains found in northeast of u.s are similar in age and structure as mountains, in Greenland and Scandinavia.
STRUCTURE OF THE EARTH
Pressure and temperature increase as you move toward the center of the earth.
CRUST- the outermost layer of the earth.
continental crust- composed mainly of granite, low in density.
oceanic crust- composed mainly of basalt, high in density.
lithosphere- crust and uppermost solid part of the mantle.
asthenosphere- underlies the lithosphere, composed of partially molten rock.
moho- the boundary between the crust and the mantle.
mantle- the layer of molten rock extending from the crust downward 2850 km.
outer core- between mantle and inner core, composed of iron and nickel.
inner core- solid iron and nickel located at the center of the earth.
PLATE TECTONICS
plate tectonics is the study of the formation and movement of plates.
plates are composed of lithosphere (continental=thick, oceanic= thin) 12 major and several minor plates.
EARTHQUAKES
an earthquake is a shaking of earth's crust cause by the release of energy.
reasons why they occur:
eruption of a volcano
the collapse of a cavern
the impact of a meteor
sudden movement along a plate boundary cause by the release of stress.
DEPTH OF EARTHQUAKES *
focus- the point on a fault plane at which the first movement occurs.
epicenter- the point on earths surface directly above the focus.
EARTHQUAKE WAVES *
three basic kinds of waves
primary (P)waves- back and forth wave motion; can travel through any material; fastest.
secondary waves(S)- side to side wave motion; can travel through solids but not through liquids or gases.
surface waves(L)- form when p+s waves combine. form when p + s waves reach the surface which move slowly like ripples on a pond:slowest.
LOCATING A EARTHQUAKE *
seismograph- the instrument that detects and records earthquake waves.
seismogram- the sheet which displays the zig-zag trace if earthquake waves.
*P-Waves always arrive before S-Waves*
P and S wave arrival time difference can then be used to determine the distance from the recording station to the epicenter.
LOCATING AN EPICENTER
Triangulation- we then use the epicenter distance's from at least 3 recording stations to locate the epicenter.
You need to next measure the distance to scale and drawing a circle from each station. Once 3 circles are drawn they will intersect at one common point. This location is the epicenter.
SHADOW ZONE*
The shadow zone is a wide belt around earth on the side opposite the focus of the earth quake. Seismic stations receive neither P nor S waves.
The cause of the shadow zone is the Earth's outer core.
S-waves can not travel through the liquid outer core. While P waves are refracted (bent) in a smooth arc back to the surface.
The Ring of Fire
-Volcanism
-Magma- molten rock underground.-Felsic- magmas with relatively high silica are thick, light colored, and slow moving.
-Mafic- relatively low silica content, thinner, darker, and flow more easily.
-Magma contains dissolved gases that are given off as the magma erupts. The most important of these gases are water vapor, carbon dioxide, and sulfur.
-Magmas containing large amounts of dissolved gases tend to produce more explosive eruptions.
-Lava- molten rock that has reached the surface.
-Felsic Lava- thick and stiff called AA lava. Produce explosive eruptions.
-Mafic lava- thin and fluid called pahoehoe lava. Lave pours out and smoothly (less explosive)
Lava Fragments
Tephra- solid fragments of lava produced from explosive eruptions.
Kinds of Eruptions
Rift Eruptions- Occur at long, narrow fractures in the crust such as mid-ocean spreading centers.
When lava flows out smoothly and fluidly it forms a volcanic mountain with a broad base and gently sloping sides called a shield zone.
Subduction boundary eruptions are the result of thick magma that forms at Subduction boundaries.
These eruptions are more explosive due to the large amounts of gases in the magma.
Forms a cinder cone with very steep sides.
Hot Spots
Hot spots are areas of volcanic activity in the middle of the lithosphere plates.
Similar to rift eruptions. Smooth flowing lava and shield cones.
WEATHERING AND EROSION
Weathering- The breakdown of rocks at or near the surface of the earth.
Physical Weathering- the breakdown of rock into smaller pieces without chemical change.
Ice Wedging (frost action)- Water held in the cracks of rocks wedges the rock apart when it freezes.
Root Wedging (plant action)- Tiny roots grow into cracks in the rock and then as the root grows the rock splits.
Exfoliation- when large masses of rock, mainly igneous, are lifted up to the surface the relief of overlying pressure causes the rock to expand. Upward expansion leads to curved breaks which may peel off in layers
Chemical Weathering- The breakdown of rock through a change in mineral or chemical composition.
Oxidation- The chemical reaction of oxygen with other substances. Iron is most easily attacked resulting in rust (iron oxides)
Carbonic Acid- When carbon dioxide dissolves many common minerals.
Minerals Resistance to Weathering- Different minerals and rocks have different physical and chemical properties which
allow them to weather at different rates.
• Quartz- almost unchanged by chemical weathering. It is hard and does not have cleavage so it also resists mechanical weathering.
• Feldspar, Mica, Calcite, and Gypsum- affected by both types of weathering and will break down into clay with calcite and gypsum dissolving and being carried off in solution.
Sedimentary Rocks-
• Shale- is the least resistant to mechanical weathering
• Sandstone- is the most resistant to mechanical weathering
- The type of cement which holds the sandstone together determines how resistance the rock is Calcite- low resistance and Silica- high resistance.
-Rocks which contain the mineral calcite, such as Limestone or Marble are somewhat resistant to mechanical weathering but is the least resistance to chemical weathering.
Factors Affecting Rate of Weathering!
Exposure- the closer to the surface of the earth, the faster it will weather.
- Rate and type of weathering depends on exposure of rocks to air, water and the action of living things.
Surface Area- The greater surface area exposed to the weathering the faster the rate of weathering.
Two samples of the same material having the same mass can have different surface areas. If one sample is a large piece of marble with a mass of 50g, and the other is 50g of many small pieces of marble. The smaller size pieces will
have the greater surface area.
Climate effect on Weathering.
Chemical weathering- is usually greater in warm, moist climates.
Physical Weathering- usually greater in moist areas with temperature variations (cold and warm)
Soils- soil is made of loose, weathered rock and organic material in which plants with root can grow. The rock material is composed sand, silt, and clay.
Parent material- the material from which a soil is formed.
Residual Soil- soil that has the bedrock beneath the soil as a parent material
Transported Soil- soild formed from deposits left by winds, rivers, and glaciers.
A-Horizaon (Top Soil)- darkest color due to organic material.
B-Horizaon (Subsoil)- 1) clay is washed to the subsoil
2) May contain soluble minerals, such as calcium and magnesium carbonates
3) color is usually red- brown from iron oxides that form above and wash down
C-Horizon- Made of slightly weathered parent material (rock fragments)
A-horizon Topsoil
Darkest color due to organic material
B-Horizon Subsoil
1) Clay is washed to the subsoil
2) May contain soluble minerals, such as calcium and magnesium carbonates
3) Color is usually red-brown from iron oxides that form above and wash down
C-Horizon
Made slightly weathered parent material (rock fragments)
UN-WEATHERED BEDROCKS
Climate
Tropic soils from in areas with high temperatures and heave rainfall. A thick infertile soil profile is results of heavy rain
Grassland soils from areas with enough rainfall for the heavy grass, but not trees/ About 1 meter thick and fertile
Forest soils form in humid regions with cool seasons. Soil profile is less then 1 meter thick with the developed A, B, and C Horizon
Desert soild form in very dry climates. Soil profile is a few centimeters
Weathering And Erosion
MASS MOVEMENTS
Movements of loose earth material down a slope.
Gravity is an aid in weathering and erosion. Steep slopes weather to gentle slopes.
Creep- slow, imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to lean downhill.
Water in the soil is what adds the weight.
Mudflow- the rapid movement of a water saturated mass of soil.
As the earth on a hill moves from under the tree, the tree continues to grow up towards the light.
Slump- occurs when a section of land moves downhill as a while because of a plane of weakness in the underlying soil.
Landslide- sudden movement of a mass of bedrock or loose rock down the slope of a hill or mountain. (Avalanche- snow, ice, rock, and soil.)
Talus- is a pile of rock fragments at the base of a cliff.
Wind Erosion
Wing transports materials by causing their particles to move in different ways.
Suspension- a method of transport by which strong winds cause small particles to stay airborne for long distances.
Saltation- causes a bouncing of motion of larger particles. Saltation accounts for most sand transport by wind.
Wind erosion is greatest in arid climates (low precipitation) with little vegetation. (Deserts and seashores)
Abrasion is a process of erosions found in wind, water, and ice. It occurs when particles such as sand rub up against the surface of rocks or other materials.
Ventifacts are rocks shaped by windblown sediments.
Wind deposition occurs in areas where wind velocity decreases.
Dunes are piles of windblown sand that have a gentle side and a steep side.
The gentler slope occurs when the side of which the wind is blowing (windward side). The steeper lope occurs on the side protected from the wind (leeward side.)
Loess- thick deposits of fine lightweight particles (Silt, Clay) that are carried by the wind in great quantities of long distances, they are some of the most fertile soils.
GLACIERS
FORMATION OF A GLACIER
Glaciers are accumulations of ice large enough to survive summer melt- forms from snow under pressure, which turns to ice.
Snow line- the lowest level that permanent snows reach in summer.
Highest near the equator.
Firn is granular ice material formed in snow fields from freshly fallen snow become compressed and recrystallizing.
The lower layers become ice and begin flowing downward or outward because of overlying pressure.
Alpine Glaciers (valley glaciers)
Occur in mountain regions above the snow line
Flow downhill and carve out U-shaped valleys.
Continental Glaciers
A glacier that spreads over a wide geographic area. Form in polar areas where the snowline is close to sea level and wide area is above the snow line. (responsible for much of the landscape in NY.)
20,000 years ago, a huge ice sheet, originated in Canada, covered New York State.
The overlying weight of snow and ice causes grains of ice to partially melt and refreeze. As this happens ice grains slip past each other and move downhill.
Glaciers move more rapidly at the surface than at the base and faster at the center than at the sides. Friction with the valley walls slow the flow.
Flows at a slow rate of a few CM to several meters per day.
Crevasses are cracks across the width of the glacier that form when glaciers move over steep slopes.
Ice front is the end of a glacier.
The ice front is the STATIONARY as long as the rate of movement and melting are equal.
A glacier RECEDS when it melts faster than normal.
A glacier ADVANCES when the rate of movement is greater then the rate at which it melts.
Pieces of rock are picked up as glaciers move and then are dragged along the bedrock and/or valley wall.
Fine sand acts as sandpaper and POLISH the bedrock.
Larger sediments leave long parallel scratches called STRIATIONS.
STRIATIONS:
Calving is when blocks of ice break off into the sea.
The finger lakes of New York were formed as advancing ice deeply scoured out valleys.
Glacial troughs are formed when a glacier carves out a valley forming a U-Shaped valley.
Valley glaciers leave sharp mountain tops while continental glaciers leave rounded tops.
Here are a few depositional features of glaciers:
Moraine is a glacial deposit of unsorted tock material.
Ground moraine- carried along the bottom
Lateral Moraine- long lines of rock pieces along the valley sides.
Medial Moraine- when two glaciers come together and there lateral moraines join together.
Cirque- a steep-walled semicircular basin in a mountain; may contain a lake.
Arete- a sharp narrow ridge found in rugged mountains.
Horn- a steep mountain peak caused by several glaciers carving different sides of the same mountain
Col- a break in an arete (mountain pass)
Truncated spur-occurs when the action of a glacier does not follow the original course of the river that wound round interlocking spurs.
Tarn- a small lake at the base of a cirque.
Hanging valley- a tributary valley that joins a main valley where the latter has been deepened, usually by glacial erosion.
Crevasse- a deep fissure.
Roches Moutonees- (resting sheep) an outcrop of bedrock which has become elongated. Sculpted by a glacier one side is smooth and the other is left rough.
Striations- a series of ridges, furrows or linear marks on a rock or other object that show which way the glacier was moving.
Drift- A load of rock material transported and deposited by a glacier.
Till- unstratified soil deposited by a glacier; consists of sand and clay and gravel and boulders mixed together.
Moraine- accumulated earth and stones deposited by a glacier.
a) lateral- forms along side of a glacier
b) medial- merging lateral moraines of two glaciers form a moraine in the middle of the glacier.
c) ground- a melting glacier deposits till in a thin layer over a broad area.
d) recessional- deposits of till that form at the end of a glacier as it retreats.
e) terminal- the end moraine found at the farthest advance of a glacier.
outwash plain- A broad, outspread flat or gently sloping alluvial deposit of outwash in front of or beyond the terminal moraine of a glacier.
kame- an irregularly shaped hill or mound composed of sand, gravel and till.
kettle- Bowl-shaped lakes created by large ice blocks, which formed depressions in Earth's surface.
drumlin- a mound of glacial drift.
rock flour- consists of clay-sized particles of rock, generated by glacial erosion or by artificial grinding.
erratics- Boulders carried long distances by the glaciers and deposited when the glacier melted.
esker- a long winding ridge of post glacial gravel and other sediment; deposited by melt water from glaciers or ice sheets.
Erosion- is the process by which earth materials are moved by natural agents like water, wind and ice.
Running Water
Running Water is the most effective agent of erosion.
The SUN is where running water gets its energy.
Rocks are weathered both Chemically and Physically by running water.
PHYSICAL
ABRASION is the term given to the use of sand, pebbles, and even boulders are cutting tools to grind away at the stream bed. During this process the "tools" themselves wear down.
CHEMICAL
The water dissolves soluble minerals.
Rivers carry rock materials in three ways.
Solution- This is material that is dissolved from the bedrock. Most commonly found in solution are compounds of calcium and magnesium.
Suspension- When small rock particles, such as clay silt and fine sand, are kept from sinking by the turbulence of the stream. This gives the water a muddy look.
Bed Load- sand, pebbles, and some boulders, which most along the stream bed.
CARRYING POWER
Carrying Power is indicated by both the total amount of sediment in a stream and by the side of the particles being moved.
The stream discharge and speed will determine the carrying power of the stream.
Discharge- is the volume of water flowing past a given point at a given time.
Speed- is generally determined by the steepness, or gradient, of its bed.
A stream moving at high speed with a high discharge can carry much larger sediments then a slow moving stream. Example: Spring time snow melting and excessive rain.
THE RIVER VALLEY
Rivers tend to have a V-Shape valley because they tend to flow at high speeds and dig into the stream bed.
BASE LEVEL- is the lowest level a river can cut into its bed.
To form a permanent stream rain water must flow down a slope and dig deep enough to cut into the water table. This wearing away of the land to form a stream valley is called head-ward erosion.
A divide is an area of high land that seperates one river valley from another.
On either side of a divide a river system may form.
Watershed- is all of the land that drains into the river either directly or through its tributaries.
WATERFALLS
^ Water flowing over a steep cliff will result in a waterfall. Waterfalls are not permanent structures.
Undermining- is the erosional process occurring at the base of a waterfall. Here water carrying sediment plunges down and back into the stream ed and cliff below. This causes the rocks at the top of the falls to overhang. Over time this overhang will collapse and the stream will move back towards its source.
RIVER DEPOSITION
Deposition occurs when a strean either decreases in speed or discharge.
Generally the speed decreases when its slope decreases or its bed widens. The greatest loss of speed occurs when a river empties into a quiet body of water.
A decrease in discharge would occur if a river traveled through an area with low precipitation.
As rivers begin to decrease their slope they move slower and will begin to move side to side.
As the valley wall on either side is eroded the valley floor is widened.
A Flood Plain is the widened valley floor area which will accumulate water during times of excess rain when the rover floods.
EROSION AND DEPOSITION IN A RIVER
Meanders are broad curves in tge river (each bend or turn)
Erosion is greatest on the outside of a meander where water is flowing the fastest. (cut bank)
Deposition is greater on the inside of the meander where the water flows slower. (fill bank)
Oxbow Lake- Meanders can only become so large before they break through into another meander. The river then deposits mud and silt along the end of the abandoned meander. The now separated meander becomes a lake.
Running water deposits well-sorted particles
Vertical Sorting- When sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top.
Horizontal Sorting- When rivers empty their sediments into quiet bodies of water. Particles are sorted by size with larger particles being found closer to the shore and smaller particles being carried out into the body of water to be deposited.
Delta- a fan shaped deposit of sediment at the mouth of a river.