Geology Exam Review: Mountain Building
Andean-type mountain building (ocean/continent):
Active continental margins , Subduction zone forms ; Deformation process begins: Continental volcanic arc forms Accretionary wedge forms
How are Aleutian and Andean mountains different?
Aleutian: ocean ocean subduction, volcanoes form at ocean, basaltic magma; Andean: ocean/continent subduction, volcanoes dorm on land (continental volcanic arcs), mountains, rhylotic magma
What is fold?
Changes due to compression, Material may bend, Rocks bent into waves, Compressional forces shorten & thicken crust; ex. metamorphic rock
what is isostasy?
Concept of a floating crust in gravitational balance , When weight is removed from the crust, crustal uplifting occurs ,Process is called isostatic adjustment (inbalanced like a mattress)
Buoyancy and the principle of isostasy :
Evidence for crustal uplift includes wave-cut platforms high above sea level
What are joints?
Fractures without displacement, rocks in the outer-most crust are deformed; no movement/displacement
Continental collisions
Where two plates with continental crust converge (e.g., India and Eurasian plate collision ,Himalayan Mountains and the Tibetan Plateau )
What is Horst and Graben?
a series of normal faults. graben: low points, horst: high points
What is deformation?
all changes in original form and/or size of a rock; Most occur along plate margins
What are the types of folds?
anticline, syncline, monocline, dome,
What are the types of faults?
dip-slip fault , normal fault
Faults breaks in rocks with _________.
displacement
What are strike slip faults?
dominant displacement is horizontal and parallel to strike; produced by shearing forces; transform fault:cuts through the lithosphere, associated with plate boundaries, plates moving past each other
What is a syncline fold?
downfolded rock layers
Parts of the dip-slip fault: The ________ wall is the rock above the fault surface. The ______ wall is the rock below the surface.
hanging wall and footwall
What is a normal fault?
hanging wall block moves down caused by tensional forces
What is a reverse and thrust fault?
hanging wall moves up, caused by strong compressional stresses
What is a monocline fold?
layered material layed down so you get a big step.
What is orogeny?
mountain building
What is a dip-slip fault?
movement along the dip of fault plane because of tensional forces
What are the Factors that influence rock strength?
Temperature and confining pressure , Rock type , Time
Continental accretion
Third mechanism of mountain building, Small crustal fragments collide with and accrete to continental margins ,Accreted crustal blocks are called terranes , Occurred along the Pacific Coast
What is a basin?
circular, or slightly elongated, down-warped displacement of rocks, youngest rocks are in the center
What is a dome?
circular, or slightly elongated; unwarped displacement of rocks; oldest rocks are in the center
What is faulting or faults?
cracking rocks; breaking of rocks due to tensional, shear or compressional force
________ refers to processes that collectively produce a mountain belt .Mostly at _________ boundaries
orogenesis; convergent boundaries
What is an anticline fold?
shape like an "A" ; upfolded, or arched rock layers
Aleutian islands:
subduction plates (plates sliding) , ocean/ocean subduction, get volcanoes formed in the ocean, volcanic islands, more basaltic magma
Andean mountains:
subduction plates (plates sliding, ocean/continent subduction, volcanoes form on land (continental volcanic arcs), some mountains form, rhylotic (more sticky explosive)
Anticlines and synclines can be:
symmetrical, assymetrical, and overturned - one limb is tilted beyond the vertical
What are the factors that determine how rock deforms?
they either fold or fault (break)
