Landforms Flashcards
What is a landform?
Feature of the surface of the earth
Positive landforms:
mountains, hills
Negative landforms:
canyons, valleys
What is the difference between a mountain and a hill:
amount of relief/elevation
What is the difference between a canyon and a valley?
canyon: super steep walls
valley: not steep
Flat landforms:
plains, plateaus
A collection of landforms in an area make up a given terrain
- Some are flat, or undulating/rolling or rugged
- The relief (change in elevation) across a terrain may be described as: high, moderate, or low
- The slopes in these terrains may be described as: steep, moderate, or shallow
Terrain types + description
- Mountainous terrains have high, rugged relief and steep slopes
- Hilly terrains have moderate, rolling relief with gentle slopes
- Flat terrains may slope gently or undulate
- Some terrains are mixed
The details of terrains (distribution of landforms) are shown on:
topographic maps
How do landforms form?
- Geologic processes cause portions of the land surface to move up or down relative to adjacent areas
- Upward movement = uplift
- Downward movement = subsidence
A major cause of uplift and subsidence is:
plate tectonics, which squeeze and stretch the lithosphere in different places around the world
Ocean-continent and continent-continent convergence produce:
mountains through squeezing the crust, can also result in volcanism and volcanic uplift
Volcanic uplift is the result of:
material being added to the surface, hot rocks (at and below the surface) take up more space
Uplift can also happen at divergent boundaries:
- new material added to the surface, hot rocks take up more space, newly added material moves away from ridge then cools and contracts
- Cooling = decrease in elevation
What is subsidence caused by?
Stretching the crust (rifting/divergence) or when a load (downward force) is added to the crust
Subsidence steps for squeezing the crust
- Initially hot, rising rocks cause uplift
- Stretching pulls the lithosphere apart, causing it to thin and the centre to drop (subsidence), producing a rift valley
- Oceanic crust is thinner than continental crust
- Continued divergence may produce a new ocean
What happens when a load is added onto the crust?
- Crust flexes downward in response to load = subsidence
- Can also occur when materials are removed from the crust i.e oil/natural gas extraction, mining, dissolution of limestone, groundwater related
Uplift and subsidence produce:
relief (differences in elevation) across a terrain
Wherever relief develops, rocks are subjected to
weathering and erosion, weathered and eroded materials eventually get deposited
The shape of landforms are modified by:
weathering, erosion, and deposition
Erosion and deposition redistribute:
Sediment on Earth, stripping it from high spots and piling it up in low spots
Even though weather, erosion, and deposition have operated on Earth for billions of years, Earth is not flat. Why?
Ongoing uplift and subsidence continue to move rocks up and down, changing the shape of the land
Landforms produced through plate tectonics are called
tectonic landforms
Landforms produced through volcanism are called
volcanic landforms
Landforms produced through erosion are called
erosional landforms
Landforms produced through sediment deposition are called
depositional landforms
What are the six factors that control the formation of landforms?
- Eroding agent
- Relief
- Climate factors
- Substrate composition
- Life activity
- Time
Eroding agent
- moving water, air, and ice produce landforms with different shapes because they carve into the land and carry the debris differently
- i.e Glacial Valley = U-shaped, River Valley = V-shaped
- Glacial deposits: poorly sorted, range of sizes. Wind deposits: well-sorted, small clasts
Relief
the height and steepness of slopes determines whether rocks or soil will stay in place or tumble downslope, and how fast (controls velocity of water and ice).
Climate factors (wind, rain, snow, temp, etc.)
- determine whether flowing ice, wind or water is the main agent of erosion and deposition.
- affects the rate of weathering (warmer = faster weathering)
Substrate composition
- Some earth materials are more resistant to erosion than others and can form steep cliffs.
- Weak materials collapse and form gentle slopes.
Life activity
- Some organisms weaken earth materials by burrowing or digesting them; others help bind loose materials together (tree roots).
- The landforms that form in an area may be influenced by biological activity.
- Humans alter the landscape and influence landform development i.e dams
Time
landscapes evolve over time in response to continued erosion or deposition
