MOUNTAIN BUILDING

Factors Affecting Deformation of Rock Factors that influence the strength of a rock and how it will deform include temperature, pressure, rock type, and time. Deformation is a general term that refers to all changes in the original shape and/or size of a rock body. Stress is the force per unit area acting on a solid.

Rock Type Mineral composition and texture of a rock also greatly affect how it will deform.

Time In nature small stresses applied over a long period of time plays an important role in the deformation of rock.

Types of Stress The three types of stress are tensional, compressional and shear. Tensional – when rocks are pulled in opposite directions Compressional – when rocks are pushed together or squeezed. Shear – when rocks are distorted from different pulling.

Types of Stress

Folds Types of folds: Anticline– upfolding, or arching, of rock layers. Syncline–linear downfolds in sedimentary strata.

Folds

Folds

Faults Types of faults: Normal–hanging wall block moves down (gravity) Reverse–hanging wall block moves up the footwall block Strike slip–side to side

Faults

Types of Mountains

Folded Mountains Mountains that are formed primarily by folding. Compressional stresses

Fault-Block Mountains Large blocks of crust are uplifted and tilted along normal faults.

Domes and Basins Uplifting produces a circular or elongated structure, the feature is called a dome.

Mountain Formation

Plate Boundaries What types of mountains are associated with convergent plate boundaries? Volcanic Mountains Folded Mountains With divergent plate boundaries? Fault Mountains

Ocean-Ocean Convergence Ocean-ocean convergence mainly produces volcanic mountains.

Ocean-Continental Convergence The types of mountains formed by ocean-continental convergence are volcanic mountains and folded mountains. An accretionary wedge is the accumulation of different sedimentary and metamorphic rocks with some scraps of ocean crust.

Continental-Continental Convergence At a convergent boundary between two plates carrying continental crust, a collision between the continental fragments will result and form folded mountains.

Divergent Plate Boundaries The mountains that form along ocean ridges at divergent plate boundaries are fault type mountains.

Non-Boundary Mountains Not all mountains are formed by plate boundaries. Some are formed by hot spots or regional extension or stretching.