Quiz 11-Bonus! (9:30-9:35 AM)
UNIVERSITY OF SOUTH ALABAMA
GY 111: Physical Geology
Lecture 30: Mountain Building 1:
Isostacy and Thrusting
Last Time
Last bit about Metamorphism
A) Metamorphic Facies
B) Retrograde Metamorphism
C) Shock Metamorphism
Web notes 29A: Metamorphic Facies
Web notes 29B: Retrograde Metamorphism
Metamorphic Facies
Temperature
High
Low
Eclogite facies
High
Granulite
Greenschist
Pressure
Amphibolite
Hornfels facies
Zeolite
facies
Metamorphic Facies
Temperature
High
Low
Zeolite
facies
Hornfels facies
slate
Eclogite facies
High
Granulite
Amphibolite
Greenschist
Pressure
phyllite
gneiss
Metamorphic Facies
Temperature
Pressure
Low
High
High
Metamorphic Facies
Temperature
Pressure
Low
High
High
Today’s Agenda
Mountain Building 1
A) Distribution of mountain belts (the return of plate tectonics)
B) Isostasy and the Rock Cycle (again)
C) Thrust Faults in the Rockies (movie)
Web notes: 30
Mountain Belts
Mountain Belts
Mountain Belts
Mountain Belts
New Mountains
Old Mountains
Mountain Belts
Northern
Transect
Southern Transect
Mountain Belts
The older the mountain range, the more time erosion and
weathering has had to destroy the mountains.
Mountain Belts
The older the mountain range, the more time erosion and
weathering has had to destroy the mountains.
The northern Appalachian Mountains are older than the
southern Appalachian Mountains (500 MA versus 300 MA), so
it stands to reason that they would be more eroded.
Mountain Belts
The older the mountain range, the more time erosion and
weathering has had to destroy the mountains.
The northern Appalachian Mountains are older than the
southern Appalachian Mountains (500 MA versus 300 MA), so
it stands to reason that they would be more eroded.
The surprising thing is that the southern Appalachians are still
mountains after 300 Million Years of erosion….
Why are the mountains still there?
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
Styrofoam sheets on water
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
erosion
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
isostasy
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
erosion
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
isostasy
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
erosion
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
isostasy
Isostasy (Isostacy)
The depression of the
asthenosphere beneath
mountain belts due to loading
followed by rebounding as
erosion occurs.
Erosion
Isostasy (Isostacy)
When you build up mountains, depression of the asthenosphere
produces “continental roots” below the continental crust
Isostasy (Isostacy)
Isostasy will continue as long as continental roots still exist.
Once isostasy stops, the mountains will get completely eroded
away (it takes about 500 MA for this to occur).
The Rock Cycle
Mountain belts involve all types of rocks and minerals and all
types of geological processes.
For example, consider the Himalayan Mountains
The Rock Cycle
The Rock Cycle
The Rock Cycle
So in conclusion, mountain
building (and mountain erosion)
are excellent examples of the rock
cycle in action.
Incidentally, mountain building is
itself, cyclic (see you in GY 112!)
Thrust Faulting in the Rockies
Movie time
Today’s Homework
1. Start Prepping for the Final Exam
2. Poster Show (LSCB first floor: 1-3 PM: Bonus)
3. Mobile Rock and Gem Society Show (bonus)
Next Time
1.
Holiday
GY 111: Physical Geology
Lecture 30: Mountain Building 1
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.