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Mountain formation
How
Are Formed
•Convergence due to converging plates
can be either continental-oceanic
convergence, oceanic-oceanic
convergence or continental-continental
convergence.
•deformation folding and faulting of layers
Types of mountains
 Volcanic mountains
Fold- Block mountains
Erosional mountains
Folded Mountains
Volcano
-Natural vent or opening in the earth’s crust that is connect by a pipe, or conduit ,
to a chamber at a depth that contains magma
Volcanoes may be:
• active
•Extinct
•Dormant
Type of eruption
•Hawaiian-out pouring of fluid lava and little explosive activity.
•Peleean-violent eruption with viscous lava “ nuees ardentes ’’.
•Strombolian-moderate eruptions , small explosions and lava of
average viscosity.
•Vesuvian-very explosive after a dormant period with ash/gas
clouds and gas-filled lava.
•Plinian-very explosive with pyroclastics ejected in a column up
to 50kg high producing thick air fall deposits
Volcanic mountains
•found in association with mid ocean
ridge systems , plate tectonics , along
convergent boundaries.
•also known as a composite volcano,
tall, conical volcano built up by many layers (strata) of
hardened lava, tephra, pumice, and volcanic ash.
•built almost entirely of highly fluid
basaltic lava, which travel farther than
those erupted from more explosive
volcanoes
Fault-block mountains
•are formed when large areas of bedrock
are widely broken up by faults creating
large vertical displacements of
continental crust.
Grand Tetons from Jackson Lake Lodge
(WY)
Erosional mountains
•formed by wind or water wearing down
weak spots in land and carrying it away.
Non-resistant material is washed away,
whereas the stronger material remains
Rocky mountains(north
America)
Folded mountain
created when two tectonic plates
come together .
This causes them to rise out of
the earth.
These mountains are formed by
compression
•is a structure with major displacement of rock
material along a crack in a rock
Types of faults
• are based on relative movement along the cracked
rock and include horizontal, vertical,
or a combination of movements
1. Vertical or dip slip fault
•type of fault with movement along the dip of the
fault--the concepts of hanging wall and footwall are
important in defining the different types of vertical
faults
Normal fault--hanging wall moves down in respect to
footwall
Reverse fault--hanging wall moves up in respect to
footwall--a low angled reverse fault is called a thrust
fault
•Horst and graben--a wedge of land which moves up
(horst) or down (graben) between 2 normal faults
2. Horizontal or strike slip fault
•type fault with horizontal
movement along the cracked
rock--movement can be left
lateral or right lateral
3.Oblique fault
is a fault which has a major dip
slip and strike slip component
•Slickenside- a polish and
striated rock surface that
results from friction along a
fault plane.
•Striations- means linear
furrows generated from fault
movement.
striation
slickenslide
grooves
Fault breccia, or tectonic
breccia, is a breccia (a
rock type consisting of
angular clasts) that was
formed tectonic forces.
Fault breccia of the Keystone
Thrust, Red Rock Canyon
National Conservation Area,
Nevada.
Fault gouge is an
unconsolidated tectonite(a
rock formed by tectonic
forces) with a very small
grain size
Salmon-colored fault gouge and associated fault
separates two different rock types on the left (dark
grey) and right (light grey). From the Gobi of
Mongolia.