Post on 16-Dec-2015
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
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