Earth Science

1. Earth Science Chapter 5: Section 1 Surface Processes and Landscapes

2. Water and the Ground • The continuous movement of water between the atmosphere and the ground is called the water cycle. • Evaporation – changing liquid to gas • Transpiration – process plants release water into the atmosphere • Evapotranspiration – all the water released into the atmosphere by both evaporation and transpiration.

3. Water and the Ground • Once on Earth’s surface water can: • Flow along the surface as runoff • Sink into the ground (infiltration) and become part of the ground water supply • Remain on the surface as snow or ice • Evapotranspire back into the atmosphere again

5. Water and the Ground • Most precipitation that reaches the Earth’s surface infiltrates into the ground. • This can only happen if the ground is permeable (allows water to pass through it). • The more saturated the ground, the less infiltration • The steeper the slope, the less infiltration

6. Water and the Ground • Permeability is the ability of the regolith (loose soil on top of bedrock) to allow water to pass through it. • In order for the ground to be permeable, pore spaces within the regolith must be interconnected. • Material that does not allow water to pass through it is said to be impermeable.

7. Water and the Ground • As it rains, water infiltrates the regolith until it reaches an impermeable bedrock layer. • The water cannot infiltrate further, so it fills in the pores above the impermeable layer of bedrock, forming the zone of saturation. • The upper surface of the zone of saturation is called the water table. • The zone above the water table is called the zone of aeration.

9. Water and the Ground • The porosity of a material is the amount of open pore space between particles. • Expressed as a percentage of open space • Dependent upon shape, packing, and sorting. • Rounded particles have greater porosity than angular particles • Loosely packed particles have a greater porosity than tightly packed particles • Sorted particles have a greater porosity than unsorted particles. • Particle size does not affect porosity

11. Water and the Ground • Water retained by particles • Particle size of a material does not affect porosity, but it does affect the amount of water retained. • Smaller particles will retain more water than larger particles, because smaller particles have a greater total surface area.

12. Water and the Ground • Capillarity is the ability of water to rise through pore spaces. • Water can move upward through soil, much as water rises from the roots to the limbs of a tree. • In loose materials, the smaller the pore size, the greater the capillarity.

13. Water and the Ground • Runoff occurs when rain falls faster than it can seep into the ground • The factors that will increase runoff are: • Saturated pore spaces in the ground • Steep slopes • Little vegetation • Impermeable surfaces • Most runoff is carried into streams and ends up in the ocean.

14. Weathering • Weathering vs. erosion • Weathering is the chemical and physical breakdown of rocks • Weathering is a preparation for erosion • Erosion is the movement of weathered materials from one place to another • The two general types of weathering are chemical and physical.

15. Weathering • Physical weathering occurs when rock is cracked, split or broken into sediments. • Types of physical weathering: • Frost action – breakup of rocks caused by alternate freezing and thawing of water. • Abrasion – wearing down of rocks as they rub or bounce against each other. • Exfoliation – the peeling away of large sheets of loosened material. • Plant and animal action – roots grow in cracks of rocks or animals burrow through soil and rock

21. Weathering • Chemical weathering occurs when rock is broken down by chemical action resulting in the change in composition of the rock. • Oxidation - O2 chemically unites with minerals • Hydration - H2O chemically unites with minerals • Carbonation – dissolved CO2 in water forms carbonic acid & dissolves limestone • Organic Decay – acids from dead plants dissolve in water, then the water solution dissolves rocks

25. Weathering • Climate and Weathering • Physical weathering is more pronounced in moist, cold climates where alternate freezing and thawing occur. • Chemical weathering is more intense in warm, moist climates. • Usually, the more moisture available, the more weathering occurs.

26. Weathering • Weathering rates depend on 3 variables • Particle size and surface area • Larger, solid particles of rock weather more slowly than do smaller, loose pieces • Mineral composition • Harder rocks weather slower than soft rocks • Climate • Humid climates have more weathering than dry climates

27. Soils • Soil is the part of the weathered regolith in which rooted plants will grow. • Major product of weathering • Composed primarily of particles of rocks, minerals, and organic matter. • Contains solids, liquids, and gasses

28. Soils • As soils mature, they grow richer, developing a series of layers called a soil profile.

29. Erosion • Erosion is the transportation of loose sediments or rocks produced by weathering. • Residual sediment is rock that has remained in the place it has been weathered. • Transported sediment is rock that has been moved from its place of origin to another location. • Transported sediment is far more common.

30. Erosion • The major agents (forces) of erosion are: • Gravity • Running water • Glaciers • Wind • Waves

31. Erosion • Gravity • Primary driving force behind all erosional systems • When acting with another erosional agent gravity provides the kinetic energy necessary to transport sediments • Gravity acting alone, like pulling rock down a steep cliff or slope, usually results in angular rocks

32. Erosion • Running Water • Primary agent of erosion on Earth • Sediments carried by water are usually smooth and rounded due to abrasion. • Valleys carved by streams are V-shaped. • Most running water is found in streams or rivers. • A direct relationship exists between the volume of water in the stream (stream discharge) and/or gradient and stream velocity.

33. Erosion • The stream velocity is generally greatest just below the surface near the center of the channel. greatest velocity

34. Erosion • Water near the outside of a curve has a greater velocity than water near the inside of a curve. • Erosion takes place at the outside of the curve and deposition occurs at the inside.

35. Erosion • The size of particles a stream can carry increases as the stream velocity increases • Streams can carry sediments in 3 ways • Dissolved particles in a solution • Fine sediments in suspension • Larger rocks bounced, pushed, or rolled along the stream bed (saltation).

36. Erosion • Glaciers • Most of NYS has evidence of glacial erosion • Valleys carved by glaciers are U-shaped. • Rocks are unsorted, angular and may have parallel scratches or one polished side. • Like with running water, the greater the volume of ice and/or the steeper the slope, the greater the velocity and the more the glacier erodes. • Can transport the largest particles

37. Erosion • Wind • Sediments are usually angular and, although smooth, not as smooth as by running water. • Rocks are often pitted and frosted. • Like with running water and glaciers, the greater velocity the larger the particles the wind can carry.

38. Deposition • Deposition is the release of sediments from an erosional system. • Caused by the decrease of carrying power of an erosional agent. • Factors Affecting Deposition • Particle size • The settling rate of particles is determined mainly by its particle size

39. Deposition • With all other factors equal, larger particles settle faster than smaller particles because they weigh more. • In running water, very small particles remain suspended for long periods of time. • When a mixture of sediment sizes settle in still water sorting in horizontal layers takes place.

41. Deposition • Particle shape • If all other factors are equal, smooth, spherical objects usually settle faster than angular, flatter particles. • Particle Density • If particles are about the same size and shape, higher-density particles will settle faster than lower-density particles.

42. Deposition • Velocity of Transporting Medium • As the velocity decreases, there is a loss of carrying power and larger, heavier, denser particles settle out first. • Horizontal Sorting

43. Deposition • Glacial deposition • Two main types are till and outwash. • Till is unsorted rock material deposited directly from glaciers. • Outwash is rock deposited by the meltwater of a glacier and can show horizontal sorting.

44. Erosional-Depositional System • An erosional-depositional system combines the erosional processes, the transporting agents and processes of deposition. • Examples:

46. Erosional-Depositional System