Conceptual Physical Science 5 th Edition Chapter 22

This lecture will help you understand: • • The Hydrologic Cycle Groundwater The Work

The Hydrologic Cycle More than 97% of all Earth’s water is in the oceans.

The Hydrologic Cycle Earth’s waters are constantly circulating. The driving forces are: • Heat

The Hydrologic Cycle The hydrologic cycle is the set of processes that controls the

The Hydrologic Cycle Water that goes from the ocean back to the ocean makes

The Hydrologic Cycle CHECK YOUR NEIGHBOR Earth’s natural supply of fresh water comes from:

The Hydrologic Cycle CHECK YOUR ANSWER Earth’s natural supply of fresh water comes from:

Groundwater Factors that influence storage and movement of groundwater: • Porosity: ratio of open

Groundwater Permeability • Degree to which groundwater can flow through a porous material—higher permeability,

Groundwater The Water Table Water beneath the ground exists as groundwater and soil moisture.

Groundwater The Water Table The depth of the water table varies with precipitation and

Groundwater Aquifers and Springs Aquifers are reservoirs of groundwater. • Aquifers are a vital

Groundwater Aquifers and Springs A perched water table occurs when discontinuous, low-permeability layers in

Groundwater Aquifers and Springs Geologists can often use springs to locate faults, because a

Groundwater CHECK YOUR NEIGHBOR A soil with rounded particles of similar size will have

Groundwater Movement The elevation of a water table above a particular location—usually sea level—is

Groundwater Movement Darcy’s law: Groundwater flow rate = hydraulic conductivity cross-sectional area hydraulic gradient

The Work of Groundwater Flowing groundwater can alter and change features at the surface:

The Work of Groundwater Land Subsidence • Extreme groundwater withdrawal by pumping from wells

The Work of Groundwater Caverns and Caves • The dissolving action of groundwater “eats

The Work of Groundwater Caverns and Caves Groundwater has carved out magnificent caves and

The Work of Groundwater Sinkholes • Sinkholes are funnel-shaped cavities in the ground that

The Work of Groundwater Karst Regions Karst regions are characterized by soft rolling hills

The Work of Groundwater CHECK YOUR NEIGHBOR What kind of formation is this? A.

Surface Water and Drainage Systems Surface water includes streams, rivers, lakes, and reservoirs. Infiltration

Surface Water and Drainage Systems Running water shapes Earth’s surface in two opposing ways:

Surface Water and Drainage Systems Stream Flow Geometry Factors that determine stream velocity: •

Surface Water and Drainage Systems Stream Flow Geometry Average stream speed = discharge /

Surface Water and Drainage Systems Stream Flow Geometry Stream speed varies within a channel.

Surface Water and Drainage Systems Drainage Basins and Networks The land area that contributes

The Work of Surface Water Flowing surface water sculpts and shapes Earth’s surface: •

The Work of Surface Water Streamflow—two types of flow • Laminar flow—slow and gentle

The Work of Surface Water Streams transport great amounts of sediment from one location

The Work of Surface Water Erosion and Transport of Sediment Chemical Weathering: Stream water

The Work of Surface Water Erosion and Transport of Sediment Stream erosion: • Loosely

The Work of Surface Water Stream Valley and Floodplains Stream channels in high mountain

The Work of Surface Water Stream Valleys and Floodplains Stream speed plays a role

The Work of Surface Water Stream Valleys and Floodplains Meandering streams create a wide

The Work of Surface Water Deltas: The End of the Line for a River

The Work of Surface Water CHECK YOUR NEIGHBOR This picture shows an example of

The Work of Surface Water CHECK YOUR ANSWER This picture shows an example of

Glaciers and Glaciation Glaciers are powerful agents of erosion. A glacier is like a

Glaciers and Glaciation Glacier Formation and Movement A glacier is an accumulation of snow

Glaciers and Glaciation Glacier Formation and Movement • When a glacier’s ice mass becomes

Glaciers and Glaciation Glacier Formation and Movement The mass of a glacier changes over

The Work of Glaciers Glacial Erosion and Erosional Landforms Alpine glaciers develop in mountainous

The Work of Glaciers Glacial Sedimentation and Depositional Landforms When glacial ice melts, it

The Work of Air Wind blows everywhere, but its impact on sculpting the land

Surface Processes CHECK YOUR NEIGHBOR There are many erosive agents that sculpt Earth’s surface.

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This lecture will help you understand: • • The Hydrologic Cycle Groundwater The Work of Groundwater Surface Water and Drainage Systems The Work of Surface Water Glaciers and Glaciation The Work of Glaciers The Work of Air © 2012 Pearson Education, Inc.

The Hydrologic Cycle The hydrologic cycle is the set of processes that controls the circulation of water on Earth. Processes involved in the hydrologic cycle: • • Evaporation Precipitation Infiltration Runoff © 2012 Pearson Education, Inc.

The Hydrologic Cycle Water that goes from the ocean back to the ocean makes a complete loop in the hydrologic cycle. The journey is not always direct. • Water can flow as streams, rivers, and groundwater • Water can also be frozen in ice caps and glaciers © 2012 Pearson Education, Inc.

The Hydrologic Cycle CHECK YOUR ANSWER Earth’s natural supply of fresh water comes from: A. B. C. D. Ice caps. Artesian springs. Glaciers. Rain and snow. Explanation: Rain and snow deliver the water that forms ice caps, aquifers, glaciers, and streams. © 2012 Pearson Education, Inc.

Groundwater Factors that influence storage and movement of groundwater: • Porosity: ratio of open space in soil, sediment, or rock to total volume of solids plus voids— the amount of open space underground. • Greater porosity equals more potential to store greater amounts of groundwater. • Particle size, shape, and sorting influence porosity. — Soil with rounded particles of similar size has higher porosity than soil with various sizes. © 2012 Pearson Education, Inc.

Groundwater Permeability • Degree to which groundwater can flow through a porous material—higher permeability, greater potential for fluid flow. • Sediment packing and connectedness of pores influences permeability. • Hydraulic conductivity—a measure of permeability—tells us the degree to which the material can transmit water. © 2012 Pearson Education, Inc.

Groundwater The Water Table Water beneath the ground exists as groundwater and soil moisture. • Groundwater occurs in the saturated zone— water has filled all pore spaces. • Soil moisture is above the saturated zone in the unsaturated zone—pores filled with water and air. The water table is the boundary between these two zones. © 2012 Pearson Education, Inc.

Groundwater The Water Table The depth of the water table varies with precipitation and climate. • Zero in marshes and swamps, hundreds of meters in some deserts. • At perennial lakes and streams, the water table is above the land surface. • The water table tends to rise and fall with the surface topography. © 2012 Pearson Education, Inc.

Groundwater Aquifers and Springs Aquifers are reservoirs of groundwater. • Aquifers are a vital source of fresh water. • Aquifers generally have high porosity and high permeability. • Aquifers underlie the land surface in many areas. • It is important to keep this vital source of fresh water clean and contaminant free. © 2012 Pearson Education, Inc.

Groundwater Aquifers and Springs A perched water table occurs when discontinuous, low-permeability layers in an unconfined aquifer intercept percolating water above the water table. © 2012 Pearson Education, Inc.

Groundwater CHECK YOUR NEIGHBOR A soil with rounded particles of similar size will have a higher porosity than a soil with rounded particles of various sizes, because A. B. C. D. it will have a higher permeability. water flows more easily through rounded particles. smaller sediment grains will fill the open pore spaces between larger grains. poorly sorted sediment will have more open pore spaces. © 2012 Pearson Education, Inc.

The Work of Groundwater Land Subsidence • Extreme groundwater withdrawal by pumping from wells can result in lowering of the land—land subsidence. • Land subsidence is especially prevalent in areas underlain by aquifers made of sandy sediments and interbedded clays. The clays leak water to the sand, then water is pumped out, the clays shrink and compact, causing subsidence. © 2012 Pearson Education, Inc.

The Work of Groundwater Caverns and Caves • The dissolving action of groundwater “eats away” at rock—limestone in particular. • Rainwater chemically reacts with CO 2 in the air and soil, producing carbonic acid. The acidified water seeps into rock (especially limestone), partially dissolving it. © 2012 Pearson Education, Inc.

The Work of Groundwater Sinkholes • Sinkholes are funnel-shaped cavities in the ground that are open to the sky. • Sinkholes are formed in a manner similar to caves. • Sinkholes can also be formed from conditions of drought and the overwithdrawal of groundwater. © 2012 Pearson Education, Inc.

The Work of Groundwater Karst Regions Karst regions are characterized by soft rolling hills or sharp, rugged surfaces. Karst regions areas where sinkholes, caves, and caverns define the land surface. © 2012 Pearson Education, Inc.

Surface Water and Drainage Systems Surface water includes streams, rivers, lakes, and reservoirs. Infiltration of water is controlled by: • • • Intensity and duration of precipitation Prior wetness condition of the soil Soil type Slope of the land Nature of the vegetative cover © 2012 Pearson Education, Inc.

Surface Water and Drainage Systems Stream Flow Geometry Factors that determine stream velocity: • Gradient, or slope • Discharge—volume of water moving past a given point in a certain amount of time • Channel geometry characteristics — shape and size © 2012 Pearson Education, Inc.

Surface Water and Drainage Systems Stream Flow Geometry Average stream speed = discharge / cross-sectional area Stream speed is usually not constant along the length of a stream. As the stream moves downslope, the gradient decreases and the channel widens. Discharge usually increases as tributaries add water. © 2012 Pearson Education, Inc.

Surface Water and Drainage Systems Stream Flow Geometry Stream speed varies within a channel. It is slower along the stream bed (friction) and faster near the surface. • In a straight channel, maximum flow speed is mid-channel. • In a curving channel, maximum flow speed is on the outside of each bend. © 2012 Pearson Education, Inc.

Surface Water and Drainage Systems Drainage Basins and Networks The land area that contributes water to a stream is called the drainage basin. Drainage basins are separated by drainage divides. The largest drainage divides are continental divides. © 2012 Pearson Education, Inc.

The Work of Surface Water Flowing surface water sculpts and shapes Earth’s surface: • Erosion—erosive sculpting action carves the landscape • Deposition—shapes the land as sediment is deposited © 2012 Pearson Education, Inc.

The Work of Surface Water Streams transport great amounts of sediment from one location to another. Laminar flows can lift and carry only the very smallest and lightest particles. A turbulent flow can move and carry a range of particle sizes—it moves particles downstream mainly by lifting them into the flow or by rolling and sliding them along the channel bottom. The smaller, finer particles remain suspended to make the water murky. © 2012 Pearson Education, Inc.

The Work of Surface Water Erosion and Transport of Sediment Chemical Weathering: Stream water carries dissolved substances that chemically weather and erode rock. Hydraulic Action: Erosion and movement of great quantities of sediment and rock. Abrasion: Abrasion occurs when sediments and particles scour a channel. © 2012 Pearson Education, Inc.

The Work of Surface Water Erosion and Transport of Sediment Stream erosion: • Loosely consolidated particles are lifted by abrasion and dissolution. Stronger currents lift particles more effectively: • Stronger currents have “higher” energy • Lift and transport more and bigger particles • Turbulent versus laminar flow © 2012 Pearson Education, Inc.

The Work of Surface Water Stream Valley and Floodplains Stream channels in high mountain areas cut into underlying rock. Fast-moving rapids and beautiful waterfalls are characteristic of Vshaped mountain stream valleys. © 2012 Pearson Education, Inc.

The Work of Surface Water Stream Valleys and Floodplains Stream speed plays a role in erosion and deposition. In a meandering stream channel, maximum stream speed is on the outside bend of the channel—the cut bank—a place of erosion. On the inside bend, stream speed slows to create a point bar—a place of deposition. © 2012 Pearson Education, Inc.

The Work of Surface Water Stream Valleys and Floodplains Meandering streams create a wide belt of almost flat land: a floodplain. When a flood occurs, sediment is deposited in the floodplain. Large, coarse sediment creates natural levees. © 2012 Pearson Education, Inc.

The Work of Surface Water Deltas: The End of the Line for a River A delta is where a flowing stream meets a standing body of water. The flow slows down and the stream dumps sediment. The result is a fan-shaped deposit of new land. © 2012 Pearson Education, Inc.

Glaciers and Glaciation Glaciers are powerful agents of erosion. A glacier is like a plow as it scrapes and plucks up rock and sediment. Glaciers are also powerful agents of deposition. A glacier is like a sled as it carries its heavy load to distant places. © 2012 Pearson Education, Inc.

Glaciers and Glaciation Glacier Formation and Movement A glacier is an accumulation of snow and ice thick enough to move under its own weight. • Two types of glaciers: — Alpine — Continental © 2012 Pearson Education, Inc.

Glaciers and Glaciation Glacier Formation and Movement • When a glacier’s ice mass becomes about 50 meters thick, the pressure of the overlying material causes the base of the ice to move plastically—the entire mass shifts. • Also, meltwater at the base of the glacier creates basal sliding. © 2012 Pearson Education, Inc.

Glaciers and Glaciation Glacier Formation and Movement The mass of a glacier changes over time. As snow falls, accumulation makes the glacier grow. As ice melts, sublimates, or breaks off, ablation occurs. © 2012 Pearson Education, Inc.

The Work of Glaciers Glacial Erosion and Erosional Landforms Alpine glaciers develop in mountainous areas, generally confined to individual valleys. —Cascades, Rockies, Andes, Himalayas —Erosional landforms: cirque, arête, horn, hanging valley, U-shaped valley © 2012 Pearson Education, Inc.

The Work of Glaciers Glacial Sedimentation and Depositional Landforms When glacial ice melts, it drops a poorly sorted, heterogeneous load of boulders, pebbles, sand, and clay. A wide range of particle sizes is the hallmark that differentiates glacial sediment from the much-better-sorted material deposited by streams and winds. © 2012 Pearson Education, Inc.

The Work of Air Wind blows everywhere, but its impact on sculpting the land is minor. Impact is greatest where: • Strong winds blow frequently • Vegetation is sparse or absent — Plant roots keep particles together — Plants deflect wind and shelter particles • Surface particles are small — Small particles are more easily lifted and transported © 2012 Pearson Education, Inc.

Surface Processes CHECK YOUR NEIGHBOR There are many erosive agents that sculpt Earth’s surface. Overall, the erosive agent that does the most work is A. B. C. D. wind. groundwater. running water. glaciers. © 2012 Pearson Education, Inc.