impact of tectonics on landscapes

Tectonic landscapes

What impact does tectonic activity have on landscapes and why does

this impact vary?• Volcanic activity:

• • Variations in the form, type and frequency of eruption to be considered in relation to types of plate margin, vents and lava.

• • The distinction between intrusive and extrusive volcanic activity.

• • Extrusive landforms: volcanic cones the major sub-types being noted, lava plateaux, and minor forms such as geysers, hot springs/boiling mud.

• • Intrusive landforms: batholiths, laccoliths, dykes and sills.

• • Case studies are needed for the above and these must range from the small scale, e.g. for dykes and sills to the global when considering types of eruption.

• • Candidates must be made aware of landforms in the UK which are related to volcanic activity.

•

Extrusive volcanic landforms• Volcano types:

fissure eruptionfissure eruption

Mid-ocean ridge: creation of sea floor

Hotspots

• Extrusion= the upward movement of magma through the earths crust and onto its surface as lava. Extrusive volcanic landforms form once the lava has cooled and hardened.

Intrusive Volcanic Landforms

• Intrusion= the movement of magma underground into spaces that exist within rock strata. When this magma cools and hardens, intrusive volcanic landforms are created. Weathering and erosion causes these landforms to be exposed.

Batholith

• Batholith is the name given to the largest of igneous rocks that form as a result of magma forcing its way into the rock above it. When it cools it forms granite and this can be exposed due to weathering and erosion.

Stock• Stock is the name given to intrusive

igneous rocks smaller than 100km2.Laccolith

• A Laccolith is a dome of igneous rock that is formed between two layers of pre-existing sedimentary rocks. It forms a dome or mushroom shaped intrusion.

Plutons• Taken from Pluto the Greek god of the underworld. It is

a general term to describe any mass of rock formed by hardening magma underground. See above

Dike• A Dike is a vertical or near vertical sheet of

rock that is created when magma is thrust into a body of rock. Dikes cut across layers of existing rock. When exposed on the earths surface Dikes can appear as a wall of volcanic rock.

Sills

• Sills are long thin intrusions of rock that form a layer between other sedimentary rocks.

Vein• Sometimes magma forces its way through

cracks in the rock. When it cools vein like patterns may remain.

Landforms and Rock Structure

Exposed Batholiths and Monadnocks

Batholiths: huge bodies of intrusive igneous rock

• Form hilly or mountainous uplands• Monadnock: a mountain that rises out of a

surrounding plain and that develops because it consists of more resistant rock than the bedrock of the surrounding region

Tectonic landscapes created by Earthquakes

• Faults and Faulting• Rift Valleys• Ground displacement and folding

FaultsA fault is a break in the crust where slabs of crust slip past each other. The rocks on both sides of a fault can move up or down or sideways When enough stress builds on a rock, the rock shatters, creating faultsFaults usually occur along plate boundaries, where the forces of plate motion compress, pull, or shear the crust too much so the crust smashes

Strike-Slip Faults

Shearing creates this faultIn this fault, rocks on both sides of the fault slide past each other with a little up and down motionWhen a strike-slip fault forms the boundary between two plates, it becomes a transform boundary

Tectonic Landforms

Faults and Fault LandformsTranscurrent or Strike-slip Faults are produced when tectonic plates move past each other horizontally

Normal FaultsTension forces in Earth's crust causes these types of faultsNormal faults are at an angle, so one piece of rock is above the fault, while the other is below the faultThe above rock is called the hanging wall, and the one below is called the footwallWhen movement affects along a normal fault, the hanging wall slips downward Normal faults occur along the Rio Grande rift valley in New Mexico, where two pieces of Earth's crust are diverging

Reverse FaultsCompression forces produce this faultThis fault has the same setup as a normal fault, but reversed, which explains it’s nameJust like the normal fault, one side of the reverse fault is at an angle of the otherThis fault produced part of the Appalachian Mountains in the eastern United States

Tectonic Landforms

Faults and Fault Landforms

Reverse and overthrust faults are produced by compression in the crust

The Great Rift Valley

• The Great Rift Valley is a name given to the continuous geographic trench, approximately 6,000 kilometres (3,700 mi) in length, that runs from northern Syria in Southwest Asia to central Mozambique in East Africa.

Graben

• Another name for a Rift Valley is Graben (German for ditch) A graben is a depressed block of land bordered by parallel faults.

Tectonic Landforms

Faults and Fault LandformsNormal faults are produced by crustal extension

Folding

• Folding creates mountain ranges and also can influence coastal Geography.

Tectonic Landforms

Fold Belts

Compression from tectonic activity produces folds in rock strata

Anticlines: upbends

Synclines: troughs

Folds: corrugations of strata caused by crustal compression

Tectonic Landforms

Fold BeltsFolds erode to form ridge-and-valley landscape

•Ridges and valleys parallel•Folds may be plunging folds

Land deformation