INSTRUCTIONS FOR TODAY
1. Video of the Day: How the Earth Was Made: 25 Strangest Geological Formations on Planet Earth (8 min.)
Be sure to make point form notes from this video in your digital video journal. Please make sure this document is SHARED with Mr. Durk.
2. Read the following information below in Part 1: Background and Terminology. Follow all hyper-links to external websites for activities, demonstrations and videos (if applicable). Copy only KEY information (i.e. the highlighted terms) to your notebook (in google docs). The multiple choice question provided below are for your understanding ONLY.
3. Today, you have two choices for completing Module #13:
Option #1: Complete the Weathering Webquest (see below) and complete. Send your answers using google docs to Mr. Durk using the ugcloud.ca. You will need to record your answers on a separate google doc.
Weathering Webquest LINK (NOTE: This is a flash animation, so it must be completed on a desktop or chromebook)
Option #2: Erosion or Mass Movement: Case Study: Piktochart. Find a particular place in the world that is experiencing severe erosion (coastal, soil, etc.) or a famous mass movement. Create a Piktochart highlighting the issues, locations, and specific characteristics of this erosion / mass movement. You are required to use the website provided, which will mean that you will need to create an account and learn how to use the software.
DUE DATE: Submit all components to Mr. Durk before Module #14 (Tuesday May 3rd)
Weathering
Please remember to record all definitions and content in your virtual notebook. Definitions can be found by clicking on highlighted words.
Weathering is the breakdown of any rock in situ (without movement). We can classify all types of weathering into two general categories: chemical and physical.
Chemical Weathering
The three main agents of chemical weathering are dissolution, plant decay and oxidation. In each case, rock reacts with water, gases or acids to cause breakdown. Some landform features associated with chemical weathering include caves and karst topography. In general, the softer the rock type, the easier it is chemically weathered.
Karst Topography, mountains created by chemical weathering
Credit: U.S. Geological Society/photo by Monroe, W.H.
Physical Weathering
As the name suggests, this type of weathering does not involve any chemicals. There are many different types of physical weathering and they often have a greater visual effect on the landscape than chemical weathering.
Thermal Expansion
Thermal expansion, also known as onion-skin weathering occurs in deserts where hot days and cool night’s causes stress on the outer layers of rocks. The stresses then cause the outer layers to peel off.
Freeze Thaw
Freeze Thaw weathering, also known as frost wedging occurs when liquid water enters cracks in exposed rocks and is then frozen. Water expands up to 9% of its volume when frozen so this added pressure begins to crack the rock. As this process of freeze thaw continues, the cracks expand and eventually pieces of the rock may fall off.
Pressure Release
Pressure release weathering occurs when material such as soil is eroded from the surface and exposes rock. The decrease in pressure on the rock causes it to expand, and then break down.
Salt Crystal Growth
Similar to freeze thaw weathering, salt crystal growth occurs when crystal of salts, within the cracks of rocks expand. This type of weathering is normally associated with arid environments and coast lines.
Biotic Weathering
A final type of weathering and probably one of the most interesting is biotic weathering that occurs when living organisms cause the break down of rock. This may be from the chemicals produced by lichens or mosses or by pressure exerted on rock by tree and plant roots.
Erosion
Erosion in Arizona
(Credit: U.S. Geological Society/ photo by Lowman, S.W.)
Wind Erosion
(Credit: U.S. Geological Society/photo by Lowman, S.W.)
Erosion
(Credit: U.S. Geological Society/photo by McGimsey, R.G.)
Erosion is the process of the movement of solid material (rock, soil, mud, etc.) by agents such as wind, water ice. It may also occur when materials move downslope, due to gravity.
Causes of Erosion
amount and intensity of precipitation
texture of the soil
gradient of the slope
ground cover
land use
One of the most serious and long-running water erosion problems worldwide is in China, on the Yangtze River. From the Yangtze ( Yellow River) over 1.6 billion tons of sediment flow each year into the ocean. The sediment originates primarily from water erosion in the Loess Plateau region of northwest China.
Types of Erosion
This type of erosion moves rock and sediment downslope due to the force of gravity. It is also known as mass wasting, which we will look at on the next page.
Water Erosion
here are many types of water erosion depending on the intensity of rainfall. Splash erosion is caused by the impact of raindrops on soil. Sheet erosion occurs when heavy rain on bare soil carries sediment downslope. When there is more rain falling then can be absorbed, surface runoff occurs. This can produce gullying features. Finally streams and rivers cause downward erosion on high slopes forming a V pattern. In flatter areas the river will erode laterally (side to side).
River Erosion
Reproduced with the permission of the Minister of Public Works and Government Services Canada, 2006
Courtesy of Natural Resources Canada, Geological Survey of Canada
As the name suggests, this type of erosion occurs along coastlines. Continued wave action on both hard and soft coastlines will eventually cause sediment and rock to erode. This type of erosion can be increased with tidal actions. You will look more at features created by shoreline erosion in further activities.
Ice erosion is caused by the movement of glaciers, both alpine and continental. Glaciers break up the rock and transport it leaving a variety of features behind including: drumlins, morraines, and others. Again, you will study glacial features later in this unit.
This type of erosion is also known as eolian erosion. Sediment is commonly entrained by winds and is transported, but at high velocities, wind can also transport rocks. Vegetation can often impede or stop wind erosion.
Watch or listen to the clip about dust devils on Mars. This is a form of wind erosion.
Mass Wasting: Landslide
This type of erosion is also known as slope movement occurs when soil, rock and or sediment move downslope under the force of gravity.
Types of Mass Wasting
This is a long term process. It occurs as small movements of soil or rock gradually moving downslope over time. In general, the steeper the slope the faster the creep.
This happens when a large section of land slides during one movement. There is usually a well defined zone of sliding. It may also be known as a rock slide or a slump.
This occurs when excess water air and or ice causes the movement of rock and soil to exhibit a fluid behaviour. This can include avalanches, mudflows, debris flows and earth flows.
This last type of mass wasting occurs when blocks of rock fall away from a slope.
Causes of Mass Wasting
Soil and rock only as long as the gravitational forces are not stronger than fictional forces. Certain factors are able to reduce the frictional force, which causes the gravitational force to become stronger, creating mass wasting. Examples of these factors include:
seismic shaking
increased pressure from structures
increased soil moisture
reduction of roots from vegetation
undercutting of the slope
weathering by frost heave
Questions: For your own understanding ONLY.
Which of the following is not a type of erosion?
a) wind
b) rain
c) ice
d) acid
This type of physical weathering occurs because of differences in temperature daily.
a) pressure release
b) freeze thaw
c) thermal expansion
d) salt crystal growth
Salt crystal weathering is mostly likely to occur in what environment?
a) coastal areas
b) tundra
c) jungles
d) mountainous
Splash erosion involves the action of:
a) rivers
b) lakes
c) raindrops
d) waterfalls
Which is not a cause of mass wasting:
a) wind
b) increased moisture
c) earthquakes
d) frost heave