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Mountain Building
Tectonic plates of the world
ISOSTACY
Isostatic Rebound – crust
rises as a result of
removal of mass
__________________
This iceberg also demonstrates the
process of isostatic rebound.
Types of Mountains
• Folded Mountains (can cause plateaus
to form)
• Volcanic Mountains
• Faulted Mountains (Fault-block
Mountains)
• Divergent-Boundary Mountains
(Mid-Ocean Ridges)
• Uplifted Mountains (Dome
Mountains)
OROGENY
• All of the collective processes that form a
mountain range or mountain belt.
• EXAMPLE: the Laramide Orogeny
formed what are collectively known as the
Rocky Mountains.
• EXAMPLE: Alleghanian Orogeny formed
the Appalachian Mountains.
List all of the processes that
might contribute to an orogeny.
Principles of Geology
• UNIFORMITARIANISM
• James Hutton (1726-1797)
• • The geologic past can be interpreted and
explained by referring to present day processes,
given enough time.
• “The present is the key to the past”
• Then Charles Lyell (1797-1875)
popularized the ideas and is often credited
with this principle.
Principles of Geology
PRINCIPLE OF SUPERPOSITION
• Rocks are hardened layers of sediment
once laid down under water (Sedimentary
rocks only).
• Layers of rock were laid down sequentially,
oldest at the bottom.
• “In an undisturbed sequence of layered rock,
the oldest layer is at the bottom and the
youngest at the top”.
Principles of Geology
PRINCIPLE OF ORIGINAL
HORIZONTALITY
• Sedimentary rock layers form from sediment
laid down under water.
• Sediment is laid down under water essentially
horizontally.
• Rock layers were originally lithified
horizontally.
• Any tilting or folding of rock layers indicates
they have been moved from their original
horizontal position.
• Original Position and
orientation (horizontal)
• Deformed by
compression
• Weathering and erosion
at the surface
• Submergence and
deposition of new
sediment (horizontal)
Principles of Geology
Principle of Original Lateral
Continuity
sediment extends laterally in all
directions until it thins and pinches
out or terminates against the edges
of the depositional basin
Nicolaus Steno (1638-1686)
www.gly.uga.edu/railsback/1121Steno.jpg
Timeline: order the following events.
• India collides with the Eurasian Plate.
• A volcanic arc forms along the edge of the Eurasian
continent.
• Sub-continent of India moves toward Eurasia.
• Heavy sediments on ocean floor close up the Tethys Sea.
• Tibet begins to rise.
• Heavy sediment from ocean floor is pushed upward to
form mountain peaks.
• Folding of rock layers occurs.
• Weathering and erosion carve and shape the jagged peaks.
• Volcanic activity along the edge of Asia stops.
• Uplift of mountains continues.
1. Sub-continent of India moves toward Eurasia.
2. A volcanic arc forms along the edge of the Eurasian
continent.
3. Heavy sediments on ocean floor close up the Tethys Sea.
4. Heavy sediment from ocean floor is pushed upward to
form mountain peaks.
5. India collides with Asia.
6. Folding of rock layers occurs.
7. Tibet begins to rise.
8. Volcanic activity along the edge of Asia stops.
9. Weathering and erosion carve and shape the jagged peaks.
10. Uplift of mountains continues.
How do we know?
And here are the
Appalachians…
Folded Mountains
• Plates collide
• Folded
Mountains occur
in the same
manner as
crumpling a
sheet of paper
• The Himalayas
and the
Appalachians.
Folded Mountains
• Blue Ridge of the
Appalachian
Mountains
The formation of
Pangaea formed
the Appalachians
and the
Caledonians.
Faulted Mountains
• Plates interact and
blocks of crust are
either thrust upon
themselves or are
normally faulted.
• As movement
continues, mountains
build.
• Erosion (water, wind,
ice) shapes the
mountain peaks.
Faulted Mountains
The grand Tetons
b
Thrust Faulted Mountains
Basin and Range Mountains
(normally faulted)
Volcanic Mountains
• Subduction:
converging plates.
• One plate is forced
under the other
• Hot magma rises and
forms a volcano along
the subduction zone
• Where do we see
examples of this
today?
Mount Shasta
• Volcanic Mountain in
Northern California
• Common occurrence
in the “Ring of Fire”
Section 20.1
Crust-Mantle Relationships
Seamounts
Individual volcanic mountains produced by hot
spots under the ocean floor are called
seamounts. As a result of isostasy, the oceanic
crust around these peaks displaces the
underlying mantle until equilibrium is
achieved.
Stationary
Uplifted Mountains (sometimes
called Upwarped mountains or
Dome mountains
• Caused by forces within
the Earth pushing directly
up on a part of the crust
• A “bubble” of magma
rises and cools, pushing
overlying rock upward,
creating a dome.
• The Black Hills of
South Dakota