Agenda 3/21

• Warm-Up: How do you think mountains are formed? Use what you’ve learned so far about plate tectonics to make a guess.

• Notes: Mountain Building• Planet Earth: Mountains

M

MOUNTAIN BUILDING

Mountain Building Processes

• What processes build mountains?1) Volcanic activity2) Tectonic Activity

- Folding: Bending of rock-Faulting: Breaking of rock

Mountain Building

• Mountain building processes thicken the crust• Mountains can be twice as thick as the average

continental crust ( 70 km VS. 35 km)• Elevation of crust depends on thickness and

density• Mountains have deep roots that extend into the

mantle• As erosion occurs, mass is lost from the

mountain and these roots begin to rise

Isostasy: Crust-Mantle Relationships• Displacement of the mantle by Earth’s

continental and oceanic crust• Crust and mantle in equilibrium when gravity

is balanced by the upward force• Isostatic Rebound: slow process of crust rising

as a result of the removal of overlying material

Convergent Boundary Mountains

• Oceanic-Oceanic: 2 oceanic plates; one descends into mantle, melts, then magma forced upward forming island arc which thickens to form root, displaces the mantle, forming mountain peak

Convergent Boundary Mountains

• Oceanic-Continental:Plates come together, create subduction zone, produce major mountain belts due to the descending ocean plate forcing continental plate up; as crust thickens, higher and higher mountains form

Convergent Boundary Mountains

• Continental-Continental:Creates tallest mountains (Himalayas); it is the energy from the collision of these plates that that causes the crust to fold and fault; can double the thickness of the crust

Divergent Boundary Mountains

• Ocean ridges formed from rising convection cells that form in mantle; divergent boundary bulges upward form gently sloping mountain range

Non Boundary Mountains

• Uplifted Mountains: form when large regions of Earth have been slowly forced upward as a unit. (this concept is not well understood on why this happens)

Non Boundary Mountains

• Fault-Block Mountains:Form when large pieces of crust are tilted, uplifted, or dropped downward between large faults

Non Boundary Mountains

• Volcanic Peaks:Volcanoes that form over hot spots form far from any tectonic plate boundaries.