Earth's Surface Features

Dr. Pamela Gore
Georgia Perimeter College

Objectives

  1. Describe the major features of the Earth's surface including continents, oceans, and linear mountain belts.
  2. State the lowest (or deepest) point on Earth, the highest point on Earth (in terms of elevation), and the tallest mountain (distance from bottom to top).
  3. Discuss how plate tectonics controls topography (mountains, deep sea trenches, mid-ocean ridges, continental rifts, and faults like the San Andreas Fault).
  4. Relate plate tectonic movements to earthquakes, volcanic activity, formation of mountain ranges, and major topographic features.
This section addresses the following Georgia QCC standard(s)
  1. Recognizes features and characteristics of the Earth's surface
  2. Examines how land formations influence development of an area (economic).

Earth's Surface

Continents 40% (avg. elevation 840 m above SL; 2750 ft))
(Elevation of Atlanta is 1000 ft)
Seven continents (in alphabetical order):
  1. Africa
  2. Antarctica
  3. Asia
  4. Australia
  5. Europe
  6. North America
  7. South America

Ocean basins 60% (avg. depth 3800 m; 12,500 ft)
(Elevations are largely a reflection of their densities - granite vs. basalt. Basalt is more dense than granite, so the oceanic crust "sags" lower as it "floats" on the asthenosphere.)

The oceans are:
  1. Pacific Ocean (largest and deepest)
  2. Atlantic Ocean
  3. Indian Ocean
  4. Arctic Ocean
Sea level changes through time (ice caps fluctuate)

Most prominent features of continents are linear mountain belts
Circum-Pacific Belt
Alpine-Himalaya Belt

Highest point on Earth?
Mt. Everest (Himalayas) 8848 m or 29,028 ft

Most prominent features of oceans are ocean ridge systems.
Continuous belt 65,000 km or 40,000 mi
The oceanic ridge system is the longest mountain range on Earth.

Lowest point on Earth?
Mariana Trench -11,033 m or -36,198 ft
Deep sea trenches are subduction zones.

Tallest (not highest) mountain?
Mauna Loa, Hawaiian volcano
Base at -5000 m or -16,400 ft
Top at 4170 m or 13,677 ft
Height = 9170 m or 30,077 ft
Age nearly 1,000,000 years
30,077 ft/1,000,000 years = .03 ft/yr

What are the controls on topography?

Theory of Plate Tectonics
Lithosphere (Earth's rocky outer part) is divided into plates
The plates move relative to one another. The motion of the plates is due to convection (heat transfer) within the Earth.

  1. Convergent plate motion (compressional stress)
    Convergent motion means that the plates are moving toward one another.
    Convergent plate boundaries are likely to be:
    continental collisions (C-C) = mountains
    subduction zones (O-O or O-C) = deep sea trenches

  2. Divergent plate motion (tensional stress)
    Divergent motion means that the plate are moving apart from one another.
    Divergent plate boundaries are likely to be:
    Oceanic ridge spreading centers (O-O) = mid-ocean ridges
    Continental rifts (C-C) = East African rift zone, Red Sea

  3. Transform (shear stress)
    Transform motion occurs where a plate slides beside another plate.
    Transform plate boundaries are likely to be: Transform faults - most of which cut across the mid-ocean ridge.
    The San Andreas Fault is also a transform fault.

Plate movement generates earthquakes, volcanic activity, mountain ranges and major topographic features.

Seafloor spreading rates are about 5 cm/yr or 2"/yr (about the same as the rate of your fingernail growth).

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Page created by Pamela J.W. Gore
Georgia Perimeter College,
Clarkston, GA

Modified June 4, 2000; February 3, 2001; February 24, 2001.