Introduction Tectonics

Tectonics

From Wikipedia, the free encyclopedia

Tectonics, (from the Greek for "builder", tekton), is a field of study within geology concerned generally with the structures within the crust of the Earth (or other planets) and particularly with the forces and movements that have operated in a region to create these structures.

Tectonics is concerned with the orogenies and tectonic development of cratons and tectonic terranes as well as the earthquake and volcanic belts which directly affect much of the global population. Tectonic studies are also important for understanding erosion patterns in geomorphology and as guides for the economic geologist searching for petroleum and metallic ores.

A subfield of tectonics that deals with tectonic phenomena in the geologically recent period is called neotectonics

Tectonic studies have application to lunar and planetary studies, whether or not those bodies have active tectonic plate systems.

Since the 1960s, plate tectonics has become by far the dominant theory to explain the origin and forces responsible for the tectonic features of the continents and ocean basins.

There are three main types of tectonic regime

• Extensional tectonics
• Thrust (Contractional) tectonics
• Strike-slip tectonics

Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere.

Areas of extensional tectonics are typically associated with:

• The development of continental rifts, with or without the effects of mantle upwelling
• The gravitational spreading of zones of thickened crust formed during continent-continent collision
• Tensional flexures along strike-slip faults
• On passive margins where an effective basal detachment layer is present at the upper end of a linked system

Extensional structures

The main structures formed in areas of extensional tectonics are normal faults and graben structures.

Prominent examples include:

• The East African Rift, a major continental rift system
• The Basin and Range province of western North America
• The global mid-ocean ridge system
• The Dead Sea basin formed at a releasing bend along a continental transform boundary

Thrust tectonics is concerned with the structures formed, and the tectonic processes associated with, the shortening of the crust or lithosphere.

Areas of thrust tectonics are typically associated with:

• The collision of two continents or a continent and an island arc at a destructive plate boundary
• Restraining bends on strike-slip faults
• On passive margins, balancing up-dip extension, where an effective detachment layer is present

Strike-slip tectonics is concerned with the structures formed by, and the tectonic processes associated with, zones of lateral displacement within the crust or lithosphere.

Areas of strike-slip tectonics are associated with

• Continental transform (conservative) plate boundaries
• Lateral ramps in areas of extensional or contractional tectonics accommodating lateral offsets between major extensional or thrust faults
• Zones of oblique continent-continent collision
• The deforming foreland of a zone of continent-continent collision, a process sometimes known as escape tectonics