Describe the features created by glacial erosion that you might see in an area where valley glaciers recently existed.

APA Format Two questions 200 words each

Your response should be at least 200 words in length.

  1. Describe the features created by glacial erosion that you might see in an area where valley glaciers recently existed. Explain how each feature forms
  2. Your response should be at least 200 words in length.


The Ural Mountains are about the same age as the Appalachian mountains of eastern North America. How does the theory of plate tectonics explain the existence of this mountain belt in the interior of an expansive continental landmass? Compare and contrast the formation of the Ural and Appalachian mountains, given their similar age.

ES 1010, Earth Science 1

Course Learning Outcomes for Unit II Upon completion of this unit, students should be able to:

3. Identify processes that shape the Earth’s landscapes to include their role in the rock cycle. 3.1 Identify the three main external processes and how they fit into the rock cycle. 3.2 Discuss how running water, ice, and wind differ in their abilities to erode, transport, and

deposit sediments. 3.3 Identify examples of landscapes shaped by erosional forces.

4. Summarize the movement of water through the hydrologic cycle.

Reading Assignment Chapter 3: Landscapes Fashioned by Water Chapter 4: Glacial and Arid Landscapes Watch the following videos: Williams, C. [IDT-CSU]. (2015, August 7). Aquafers and groundwater [Video file]. Retrieved from Click here to access a transcript of the video. Williams, C. [IDT-CSU]. (2015, August 7). Mass wasting complete [Video file]. Retrieved from Click here to access a transcript of the video. In order to access the resource below, you must first log into the MyCSU Student Portal and access the

General OneFile database within the CSU Online Library. Bequette, F. (1997, March). Large dams. UNESCO Courier, 44+.


Sculpturing Earth’s Surface

ES 1010, Earth Science 2



Unit Lesson

The Grand Canyon is a magnificent example of the power of erosion and deposition. Ancient strata deposited over time have been exposed by the down cutting of the Colorado River. Although the powerful river is the main source of erosion, this landscape has also been shaped by mass wasting and erosion from ice and wind. In this unit, we will look at the power of erosion and how it shapes our landscapes. The Earth is never static. Although landscapes may appear to be unchanging over time, they are constantly being worn away by erosive forces. In fact, the Earth is constantly being changed by both internal and external processes. Internal processes are those related to plate tectonics (covered in the next unit), including mountain-building

processes. External processes are those related to the rock cycle, such as erosion and weathering. In many landscapes these are occurring simultaneously, as tectonic forces are slowly forcing land upwards erosion is wearing away those same surfaces. The rate at which each is occurring will determine whether landscapes are rising, static, or decreasing in height. This unit focuses on the external processes. External processes include weathering, mass wasting, and erosion. Mass wasting is the transfer of rock and debris downslope by gravity. After weathering occurs, rocks and sediment are loose and able to move. When they move as a large mass, it is referred to as mass wasting. This includes landslides, avalanches, debris flow, and rock slides. These can happen unexpectedly, but most often they are set off by some sort of trigger. These triggers can include periods of heavy rain or snowmelt, the over steepening of slopes, the removal of vegetation, or earthquakes. Erosion is the movement of rocks and sediment by an agent such as water, wind, or ice. Erosion generally occurs on a smaller scale than mass wasting and is a more constant process. Let us first look at the erosive force of running water. When we discuss running water we can divide it into two categories: streams and rivers, and groundwater. When water falls in the form of precipitation, it can either infiltrate the soil, eventually reaching the water table, or it can flow overland until it reaches a stream channel. Streams and rivers form what is known as a drainage basin. As small streams join with other streams, they will eventually form into larger rivers. As rivers join with other streams and rivers, they will eventually make it to a lake or ocean. The drainage basin or watershed is the entire area of land that contributes to the final outlet of water (see Fig. 3.8, p. 84 in your textbook). As streams and rivers erode the land around them, they carry the sediment downstream. Some materials will dissolve in the water, while fine sediments will be suspended. This suspended sediment will increase the erosive force by scouring the sides and bottom of a stream channel. Larger sediments will be moved along the bottom as bed load. When a stream or river reaches a lake or the ocean, the velocity of the water decreases and sediment is then deposited. In general, heavier sediment drops out first, followed by smaller sediments. This deposition forms what is known as a delta. On a large scale, the Mississippi River is a good example of sediment deposition. Sediments are eroded upstream, carried to the Gulf of Mexico, where they are deposited to form deltas. Because the Mississippi has such a tremendous drainage basin (roughly half of the United States), it carries huge sediment loads. These deposits form large deltas, upon which New Orleans was built. What do you think happens when dams trap sediments upstream? How do these processes shape the land? Stream and river channels carve out valleys. In steep terrain, where these channels are confined between mountain slopes, the channels will constantly erode downward. This creates v-shaped valleys between mountains and increases the slope gradient of the mountains. As the slopes increase, there can be mass wasting, which will widen the stream valley. As the stream valley widens and the stream reaches the base level, it will no longer down cut but rather start to meander, further widening the stream valley. Over time, a flood plain will develop in a wide, flat valley (see Fig. 3.24, p. 96 in your textbook). Water stored in streams and rivers account for less than 2% of the Earth’s fresh water. Groundwater accounts for 30% (with the remainder tied up in glaciers and ice sheets). Groundwater is a critical source of freshwater,

Grand Canyon landscape (High Contrast, 2007)

ES 1010, Earth Science 3



largely used by agriculture. In Chapter 3 you will learn about groundwater movement. The slow rate of recharge, combined with the over-pumping, has led to a continual drop in the water table (as much as 1 meter per year). This has led to land subsidence in many areas. Ground subsidence occurs when the extraction of groundwater leaves a void, which causes the overlaying land to drop. Other problems with groundwater are increasing sources of pollution, all of which are difficult to detect. Groundwater is less capable of erosion, since it moves so slowly and does not carry sediment. However, groundwater can play a role in below-ground erosion in areas of limestone. Where water is slightly acidic, it can dissolve calcium carbonate. Areas high in limestone and have high levels of precipitation can result in sinkholes and karst topography. Other significant erosive processes are ice and wind. Both play an important role in the rock cycle and produce many different landforms. Climate plays a crucial role in both of these erosional processes. Ice sheets were once extensive across the Earth—covering as much as 30% of the Earth’s surface. Currently, glaciers and ice sheets make up about 10%. Glaciers are formed when precipitation falls at high elevations or high latitudes. The snow accumulates when snowfall in winter is greater than melting in summer. As is accumulates, it compacts and recrystallizes. Water can be stored in glaciers for tens, hundreds, or even thousands of years. While in the form of ice, this water can do tremendous amounts of work. There are basically two types of glaciers—valley (or alpine) glaciers and ice sheets. Valley glaciers are confined to high mountains and flow in a pattern similar to a river. These glaciers can carve the mountain peaks to form unique landforms such as cirques, arêtes, and horns. Larger glaciers in mountain valleys can form u-shaped troughs (as opposed to the v-shaped valleys formed by rivers) and leave ‘hanging valleys’ where the bases of slopes are eroded away. When a glacier reaches the ocean, it is able to push its way into the bay (unlike rivers that slow and deposit their sediments). This carves channels into the water that are known as fjords. Ice sheets are much larger than alpine glaciers. The largest of these are Greenland and Antarctica. Unlike alpine glaciers that flow in one direction, ice sheets flow in all directions. The layers of ice slide over each other and over the land. Depending of the net accumulation of snow, glaciers can move anywhere from 2-800 meters a year. Evidence of glacial landscapes includes polished rock and abrasions, as well as large deposits called till. Unlike alluvial deposits, glacial deposits are not sorted by size. In fact, glaciers can move huge boulders long distances and deposit them far from their source. Much of the landscape of northern North America shows evidence of the most recent ice age: these include moraines, outwash plains, kettle lakes, and drumlins. Glaciers also changed the course of rivers (the Mississippi once flowed North to the Hudson Bay), formed ice dams to create lakes, and changed the sea level. The weight of the glaciers caused land to bow downward, and it has since been adjusting gradually. Changes in climate have reduced glaciers and ice sheets and most glaciers in Glacier National Park will likely disappear in the next 10-15 years (Lutgens & Tarbuck, 2014). Changes in climate have also increased the amount of arid lands on Earth. Once about 10% of the Earth’s surface, arid and semi-arid lands now make up about 30% of the Earth. The world’s largest desert, the Sahara, covers about 9 million square km (about 20 times the size of Nevada. Deserts are formed by unique conditions imposed by mountains and climates. Look at Fig. 4.24 in your textbook and notice that most desert regions are distributed in the sub-tropics (along the Tropic of Cancer and Tropic of Capricorn) and in the mid- latitudes. Why? We will cover this in more detail when we discuss climate in later chapters. Essentially, these are areas of high pressure formed by the heating of the Earth and its rotation. High pressure makes the formation of clouds and precipitation unlikely. In the mid-latitudes, deserts form in the interior of the continents, where mountains block moisture coming from the coast. Although arid regions have very little precipitation, desert landscapes are largely shaped by water. Precipitation, when it arrives, can quickly escalate to form powerful flash floods. With little vegetation and hard-baked soils, the land is prone to erosion. A single storm can significantly change the landscape. Most streams are ephemeral and dry up soon after a storm. The few rivers that do flow through deserts (like the Colorado River discussed above), are sustained from tributaries far upstream. During flash floods, these rivers can swell to become powerful torrents and carve the rock around it. Wind erosion, though a less significant erosional force, is more prevalent in arid regions than elsewhere. Wind is an effective agent of erosion only where there is little vegetation to anchor soil. Wind can transport

ES 1010, Earth Science 4



sediment much like a river, however it is limited in its ability to lift sediments larger than silt (sand can move through saltation, much like the bed load of a river). Unlike a river, wind is not confined to a river channel so its power is less concentrated in a single area. Wind can form sand dunes and deposit sediments in large quantities in certain areas, forming loess. Although the Earth’s landscapes appear static and unchanging, external forces of weathering, mass wasting, and erosion are continually wearing away the Earth’s crust. As we study the landscape more closely, we can begin to see clues as to how these forces shape the world around us.

References High Contrast. (2007). Grand Canyon landscape [Photograph]. Retrieved from andscape.jpg

Lutgens, F. K., & Tarbuck, E. J. (2014). Foundations of Earth science (7th ed.). Upper Saddle River, NJ:


Suggested Reading For more information regarding ground water depletion watch this CBS video: Finkelstein, S. (Producer), & Held, J. (Producer). (2014). Depleting the water [Video file]. Retrieved from The links below will direct you to both a PowerPoint and PDF view of the Chapter 3 and 4 Presentations. This will summarize and reinforce the information from these chapters in your textbook. Click here to access the Chapter 3 PowerPoint Presentation. (Click here to access a PDF version of the presentation.) Click here to access the Chapter 4 PowerPoint Presentation. (Click here to access a PDF version of the presentation.)

Learning Activities (Non-Graded) In this non-graded learning activity, we will look at how earthquakes are measured. Recall from the unit lesson that Intensity measures the damage caused by an earthquake, while magnitude measures the strength of the earthquake. In many cases, earthquakes of similar magnitude may have very different damage. This can be caused by the building structures, population, and side effects such as landslides, fires, and tsunamis. Research: Go to the USGS website listed below and select two of the world’s deadliest earthquakes (the year is not important) of similar magnitude with at most a difference of 0.2. (For example, earthquake A is 5.1 and B is 5.3). Remember that with logarithmic scales even small differences in numbers are usually large in reality—that is, an earthquake of magnitude 6 is 10 times that of magnitude 5. Summarize each earthquake, include the Richter scale rating, year, and location of each, and note the damage caused. Compare each earthquake in terms of the damage caused and look at the factors that might have contributed to the damage. Why were these earthquakes so deadly (tsunami, fire, poor construction, etc.)? Identify other factors that likely caused the differences in destruction. What additional factors could have led to higher destruction in one area versus another? Non-graded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information.

Your response should be at least 200 words in length.


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