Metamorphism Spitsbergen, Arctic Norway Rock folding Scotland Antarctica

Mineral Alignment: Foliation

Contact Metamorphism Heat from magma alters surrounding country rock. No pressure.

Regional Metamorphism Heat and pressure on a regional scale.

Folded Mtn Range

Subduction Zones

Slate to gneiss grading With increasing heat and pressure, minerals break down and recrystallize. As this happens, rock types change.

Metamorphic Grade Certain minerals are stable only at specific temperatures and pressures.

Contour Map Appalachians: Core of ancient mountain range is exposed.

Metamorphic Facies

Metamorphic Facies II Suites of minerals indicate specific range of T & P.

Appalachian Orogenesis

Shelf Sediments Accumulation of sands and muds. 10,000-15,000 feet thick.

Folded Pelitic Rocks

Folded Appalachians

Rock Behavior Under stress and strain, rocks behave in two different ways: 1)Brittle deformation. Low temperature, high pressure. Rocks fracture: faults 2) Ductile (plastic) deformation. High temperature, low to medium pressure. Rocks deform: folds

Types of Deformation

Folded Rocks

Anticlines and Synclines

Plunging Folds

Folded Appalachians Pic Plunging folds

Dome and Basin

Michigan Basin

Fault Definitions

Normal Fault Hanging wall moves down relative to the footwall. Creates gentle mountain front, not steep

Horst and Graben Basin and Range Province Normal faults Result of tensional stress -- crustal extension. The crust in this part of the world is being pushed up on from below.

Horst Photo

Reverse Fault Hanging wall moves up relative to the footwall.

Wasatch Fault Very steep imposing mountain front

Thrust Fault Low-angle (<20 o ) reverse fault. Many thrust faults do not outcrop at the surface -- they remain underground -- and are mapped seismically. Most recent ‘quakes in LA were from slippage along previously-unknown thrust faults.

San Andreas Fault

Strike-Slip Fault No vertical movement

San Andreas Fault Fault Offset stream

Appalachian Mtns Putting it all together --- Brittle and ductile deformation of rocks during the formation of the Appalachian Mountains.

Apps

World Mountain Chains

Geologic Time Scale

Mass Extinctions 75% of species extinct 90% of species extinct Why?

ELE

Impact Crater