Landforms

 

 

Landscape Characteristics
Earth’s landscapes are the results of the interaction of crustal materials, forces, climate, human activities, and time.

Landscape Regions
Landscape regions can usually be identified by the elevation of the region. Mountains, plateaus, and plains identify landscape regions.

·        Mountains have high elevation and deformed rock structures due to the great forces that occur when mountains are forming.

·        Plateaus have medium to high elevation.

·        Plains are low in elevation and usually have horizontal rock layers.

See page 2 of the Earth Science Reference Tables which explains where the three different landscape regions can be found in New York State.

 

Landscape Formation
The two major forces that oppose each other in the formation of landscapes are the forces of uplifting and erosion, also referred to as constructive and deconstructive forces.

·        The uplifting process is constructive and includes natural occurrences such as: folding and faulting, earthquakes, volcanoes.

·        This leads to erosion, which is part of the forces of deconstruction.

 

Climate also plays a large role in the formation of landscapes. Depending on location:

·        areas that are dry (arid) have very little vegetation present with large canyons.

·        humid areas will get moderate to high amounts of precipitation. ŕlarge amounts of vegetation and well-defined soil profiles. Humid areas are also known for their rounded hills.

Bedrock effects how the landscape looks according to its resistance to weathering and erosion. Stream drainage patterns are influenced by the rock beneath them. There are 4 main types of stream drainage patterns. They are known as DART: Dendritic, Annular, Radial, and Trellis:

  • Dendritic - treelike, flat relatively uniform materials.
  • Annular – eroded hill areas. Looks like a "dart board".
  • Radial – central point drainage. Ex. Mtn. or volcano. Pattern extends outward down the steep landscape from the highest point.
  • Trellis - abrupt bends in stream (90o), pattern locally influenced by faults, joints, folds.

Stream Drainage Patterns Diagram

 [click here to see the diagram and copy it (including the labels) into your notes]

 

 

See page 3 of the Earth Science Reference Tables which labels the major cities that can be found in New York State and the types of bedrock that can be found.

Compare these two maps to identify geology and landscapes.

 

Topographic Maps

 

 

Fields
A field is a region with a measurable quantity at every location.

Field Map Diagram

 [click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]

This diagram is an example of a field map. In this example, the numbers on the map represent the concentration of gasoline found at that location. So the map simply shows how much of something (in this case gasoline) is found at many locations.

 

Isolines
Isolines are lines that are drawn on a field map to connect all of the points on that map that have the same value.

40 meter Isolines Diagram

 [click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]
This image is an example of a gasoline field map with the 40 isoline drawn in.

Notice that the line connects points that all have the same value. In this example, the circle connects all of the points with a value of 40. That means that every point on that line has a value of exactly 40.

 


All Isolines Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]
This map has all of the isolines drawn in, at an interval of 10 (each line is 10 units apart) is shown to the right:

 

Topographic Maps
Contour lines are isolines that are drawn on an elevation map. These lines connect all points with the same elevation, and give a great picture of the lay of the land. The resulting map is called a Topographic Map.

Contour Lines Interval Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]
Above is an example of a Topographic Map. Notice that isolines are drawn every 20 meters to connect points with the same elevation.

 

There are several important rules to remember when reading a topographic map:

·        Close line =Steep Slope

Contour Lines Slope Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]

The steepest slopes on the map can be seen by looking for lines that are very close together. Since each line represents a change in elevation of a set amount (20 meters in this example), lines that are close together indicate steep gradients. The area circled in red is very steep, because it has many lines crowded close together.

 

 

·        Contour lines bend upstream when crossing a river

Upstream Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]

Since contour lines must remain at the same elevation, they must bend when they cross riverbeds. A riverbed drops downward, so the contour line must bend uphill to stay at the same elevation. The highlighted lines show that the direction of the Mill River must be northeast.

 

·        Highest possible elevation of a hill

Highest Elevation Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]

The highest elevation of a hill can be calculated by finding the last (highest) contour line on that hill, and then figuring out the next line that would be drawn. The highest possible elevation of the hill is just below the value of  that next line. The highest possible elevation of the hill indicated by the arrow is 239 meters.

The last line indicated on the map is 220 meters. The next line would be 240 meters (remember that the contour interval is 20 meters). Since there is no 240 meter line, the hill cannot be higher than 239 meters!

 

 

·        Depressions are shown by small marks
pointing inward off the contour line

Depressions Diagram

[click here to see the diagram, this does not have to be copied into your notes, but review it for understanding and read the text in this box]


The arrow is pointing to a depression, or hole. The contour line with the marks, or hatchers, has the same elevation as the line before it. In this case the hatchered line has a value of 140 meters, and the depression must be less than 140 meters.

 

Profiles
A profile is a picture of what the landscape would look like from the side. It is a cross section of the landscape. You should be able to identify a correct profile, as well as draw one.

(see handout “Identify a Profile”)

 

 

Adapted from: Regents Exam Prep Center  http://regentsprep.org/Regents/earthsci/earthsci.cfm

 

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