Transcript 5 Themes of Geography

Unit 2
Physical Geography
Types of Landforms
Landforms
ARCHIPELAGO
an expanse of water with many scattered islands
BAY
an inlet of the sea or other body of water usually smaller than a gulf
CANYON
Large crack in the earth formed by a river or earthquakes
The largest ones were created by moving water
CAPE
an extension of land jutting out into water as a peninsula
DELTA
low, water land that is formed at the mouth of a river
GULF
a part of an ocean or sea extending into the land
HILL
a mound of raised land that is smaller than a mountain
ISLAND
an area of land that is completely surrounded by water
ISTHMUS
a narrow strip of land that connects two large areas of land
PENINSULA
a strip of land that extends out into a body of water
PLAINS
a large area of flat land
PLATEAU
a large area of flat land that is raised higher than the land around it
Mountain
a large, tall, rocky area of land that comes up out of the earth’s surface
STRAIT
a narrow passage of water connecting two seas or two large areas of water
How Landforms Are Created
Plate Tectonics
Plate Tectonics
Large moving slabs of rock slide slowly over a layer of the mantle
The Theory of Continental
Drift
Earth ~200 million years ago
Alfred Wegener’s Evidence:
The presence of fossils only over small areas of now separate continents
PLATE TECTONICS
1.Divergence
2.Convergence
A. Subduction
3.Transform
DIVERGENCE
Divergence
Sea-Floor Spreading
Process where new oceanic crust is formed through volcanic activity and then gradually
moves away from the ridge
CONVERGENCE
CONVERGENCE
Forms mountains, e.g. European Alps, Himalayas
CONVERGENCE ZONE
CONVERGENCE ZONE
SUBDUCTION
SUBDUCTION
One of the crusts has to be Oceanic
Transform
Transform
No mountains are created
What are Hot Spots???
Volcanoes are formed by:
- Subduction
- Hotspots
What are Hotspot Volcanoes?
• Hot mantle plumes breaching the surface in
the middle of a tectonic plate
The Hawaiian island chain are examples
of hotspot volcanoes.
Volcanism is an internal force that can create new landforms
Pacific Ring of Fire
Shows plate tectonic boundaries
Shows the South American and Nazca plates colliding
Hawaii was formed by volcanic activity
Weathering and Erosion
Weathering
• Breakdown of rock at or near the earth’s surface
• 2 types of weathering
– Mechanical
– Chemical
Mechanical Weathering: no change in
chemical composition--just
disintegration into smaller pieces
Mechanical Weathering
• Types of Mechanical weathering
–
–
–
–
Frost heaving and Frost wedging
Plant roots
Burrowing of animals
Temperature changes
Frost Wedging: water freezes in a crack
and breaks it apart (MOST COMMON
TYPES OF MECHANICAL)
Frost Heaving
Plant Roots
Temperature Changes
Chemical Weathering: breakdown as a
result of chemical reactions
CaCO3+CO2+H2O ---> Ca2+ + 2HCO3-
Chemical Weathering
• The agents of chemical weathering
– WATER
– Acid rain
Water
Acid Rain
• Compounds from burning coal, oil and gas react
with water forming acids.
1908
1969
Acid rain has eaten away this limestone statue .
Erosion
The movement of weathered materials by water,
wind, or glaciers
Water Erosion
Wind Erosion
• picks up small
particles and blasts
large rocks, cutting
and shaping the rock.
Wind Erosion
Erosion by Glaciers
Glaciers can create lakes as they melt