Introduction to
Geography
Arthur Getis, Judith Getis, &
Jerome D. Fellmann
Physical Geography:
Landforms
Chapter 3
Overview
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Earth Materials
Geologic Time
Movements of the
Continents
Tectonic Forces
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Diastrophism
Volcanism
Gradational Processes
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Weathering
Mass Movement
Erosional Agents &
Deposition
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Glaciers
Waves, Currents, & Coastal
Landforms
Wind
Landform Regions
Earth Materials
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Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
Igneous Rocks
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Cooling & solidification of molten rock
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Underground molten rock is magma
Above ground molten rock is lava
Composition of magma & lava + cooling rate
determines the minerals that form
Granite, basalt, pumice, obsidian
Sedimentary Rocks
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Composed of particles of gravel, sand, silt, &
clay
Pressure & cementing processes cause
rocks to form
Large particles form conglomerates
Sand forms sandstone
Silt & clay form shale or siltstone
Organic materials form limestone or coal
Metamorphic Rocks
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Formed from igneous or sedimentary rocks
by earth forces that produce heat, pressure,
or chemical reactions
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Shale becomes slate
Limestone can become marble
Granite may become gneiss
Geologic Time
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Earth formed 4.7 billion years ago
Current landforms are often millions of years
old
Early 20th century work by geologist Alfred
Wegener on continental drift helped to
explain how landforms developed over time
Movements of the Continents
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Plate tectonics theory
Earth’s crust is outer, lighter portion of the
lithosphere
Lithosphere broken into 12 large and
numerous small plates that slide & drift over
the asthenosphere
Plate movement may be caused by
convection
Plate Boundaries
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Divergent plate boundaries
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Transform boundaries
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Plates slide by each other horizontally
Convergent boundaries
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Plates move away from each other
Plates move towards each other
Plate collisions can cause earthquakes along
faults
Convergent Movement
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Convergent plates can cause deep-sea
trenches and continental-scale mountain
ranges
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Heavy, but thin, oceanic crust tends to be forced
under continental crust
Deep trenches form at these subduction zones
Volcanoes and earthquakes are common in
subduction zones
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For example, the Ring of Fire
Tectonic Forces
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Diastrophism
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Great pressure causing plates to fold, twist, warp,
break, and compress
Volcanism
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The force that transports heated material to or
toward the earth’s surface
Diastrophism
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Broad warping
Folding
Faulting
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Escarpments
Rift valleys
Tsunami
Volcanism
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Strato or composite volcano
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Steep sides
Shield volcano
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Gentle slopes
No explosion
Gradational Processes
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Reduction of the land’s surface
Types
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Weathering
Mass movement
Erosion
Weathering
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Mechanical
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Frost action
Salt crystals
Root action
Chemical
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Oxidation
Hydrolysis
Carbonation
Mass Movement
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“Mass wasting”
Downslope movement of material due to
gravity
Accumulation of rock particles at the base of
hills is talus
Erosional Agents & Deposition
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Running water
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Amount of precipitation
Length & steepness of the slope
Kind of rock & vegetation
Forms landscapes such as deltas
Stream Landscapes
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Humid areas
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Waterfalls
V-shaped channels
Floodplains
Meandering streams
 Oxbow lakes, natural
levees, flooding
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Arid areas
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Lack of vegetation
increases erosional
forces
Temporary lakes
Alluvial fans
Deep, straight-sided
arroyos (wadi)
Buttes & mesas
Groundwater
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Aquifers form in zone of saturation
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Upper zone is the water table
Can dissolve soluble materials to form
stalactites, stalagmites, & sinkholes
Karst topography
Glaciers
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Covered a large part of the planet only 1015,000 years ago
Large body of ice moving down a slope or
spreading outward on a land surface
Can move as much as 1 meter per day
Glacial Landforms
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Glacial troughs
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U-shaped valleys
Fiords
Tarns
Cirques
Arêtes
Outwash plain
Moraines
Waves, Currents, & Coastal
Landforms
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Waves
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Longshore currents
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Deposition & erosion
Sandbars
Forms beaches & spits
Coral reefs & atolls
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Formed by the secretion of calcium carbonate by
coral organisms in sunny, warm water areas
Wind
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Abrasive action of sand & dust sculpts the
landscape
Dunes
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Barchan
Loess
Landform Regions
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A large section of the earth’s surface where a
great deal of homogeneity occurs