Crustal Deformation and Mountain Building

Behavior of rocks to stress & strain

• Elastic– Elastic limit

• Plastic• Brittle Stress

Strain

FOLDS

• Anticline vs. syncline– Hinge line (axis)– Limb– Axial plane

• Plunging fold• Structural dome• Structural basin

FOLDS

• Interpreting folds– Open fold– Isoclinal fold– Overturned fold– Recumbent fold

Faults

• Fractures in rock• Normal Faults• Reverse fault

– Thrust fault- low angle reverse fault

• Strike-Slip fault– Left-lateral vs. right-lateral

Introduction• Mountain

• Major mountain belts

• Mountain range

Characteristics of Major Mountain Belts

• Size and Alignment

• Along continental margin

• Long, arcuate chains

• Ages of Mountain Belts and Continents

–Youngest tend to be higher

–Himalayas vs Appalachians

–Craton- Oldest Continental Crust

• Precambrian Shield

Characteristics of Major Mountain Belts

• Patterns of Flooding and Faulting

–Fold and Thrust Belts

• Crustal Shortening

• Crustal Thickening

• Metamorphism and Plutonism

• Normal Faulting

Rifting

Major Orogeny

OrogenySubduction

Accretionary wedge Volcanism

Plutonism

Subduction

Collision Crustal Shortening &Thickening

Evolution of a Mountain Belt

• Accumulation Stage of Sediments– Accumulation in an Opening Ocean Basin– Accumulation along a Convergent

Boundary• Graywackes• Magmatic Arc

• Mountain Building Event- Orogeny

Evolution of a Mountain Belt

• The Uplift and Block-faulting Stage– Isostacy

• Isostatic Adjustment– Normal Faulting

• Fault-block Mountain Range

The Growth of Continents

• Crust added by accumulation & igneous activity

• Suspect and Exotic Terranes– Suspect terrane– Accreted terrane

• Exotic terrane

The Wilson cycle (named after J. Tuzo Wilson, one of the fathers of plate tectonics) refers to the cycle of ocean basin formation by rifting and seafloor spreading followed by ocean basin destruction and mountain building by subduction.