Download Bell Activity #15

Objectives
• Identify the most common types of
mountains.
• Explain the difference between uplift and
subsidence.
I. Plate Tectonics and Mountain
Building
A. Folded Mountains Folded
mountains form when rock
layers are squeezed together
and pushed upward.
B. Fault-Block Mountains
Fault-block mountains form
when this tension causes
large blocks of the Earth’s
crust to drop down relative to
other blocks.
https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcTUpJbwaLhpMHl
bW7PgbDvK7Lfd7hKo2UcJtwhGgR1MPZLtHU6-
C. Volcanic Mountains The rock that is
melted in subduction zone forms magma,
which rises to the Earth’s surface and
erupts to form volcanic mountains.
http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Images/MSH80_st_helens_spirit_lake_before_may_18
_1980.jpg
II. Uplift and Subsidence
A. Uplifting of Depressed Rocks
Uplift often happens when a
weight is removed from the crust.
B. Subsidence of Cooler Rocks
Rocks that are hot take up more
space than cooler rocks. The
farther the lithosphere is from the
ridge, the cooler and denser the
lithosphere becomes. Because
the oceanic lithosphere now takes
up less volume, the ocean floor
subsides.
C. Tectonic Letdown Subsidence
can also occur when the
lithosphere becomes stretched in
rift zones.
http://upload.wikimedia.org/wikip
edia/commons/thumb/4/45/East
_rift_zone_kilauea.jpg/300pxEast_rift_zone_kilauea.jpg