Effects of intrusive

igneous activity and

earthquakes on landscapes

Intrusive rocks tend to be coarse grained, since the magma cools slowly and has sufficient time to form large crystals. Extrusive igneous rocks cool rapidly at the earth’s surface, producing fine grained or glassy rocks. Basalt is fine grained because it cools very rapidly, whereas gabbro and granite are coarse grained because they have cooled slowly.

laccolith

batholith

dyke

sill

Batholiths: Largest mass of magma crumbling in the crust. An example is the Stone Mountain of Georgia. Sills: Sheets of magma intruded onto bedding planes of sedimentary rocks. Dykes: Wall like features formed when magma cuts across several bedding planes. Pipes: The stems of volcanoes. Laccoliths: Dome shaped layers of magma formed when magma encounters rock more resistant at its sides than its centre. Lopoliths: Bowl shaped layers of magma formed when magma encounters rock more resistant at its centre than its sides

http://homepage.usask.ca/~mjr347/prog/geoe118/geoe118.012.html

Hadrian’s Wall built on the Great Whin Sill – natural defensive site with scarp (steep ) slope facing Scotland and easy access dip slope on the English side

High Force waterfall is exists because the hard rock outcrop of the Great Whin Sill cuts across the course of the River Tees

The Whin Sill is a tabular layer of igneous rock, or sill, in County Durham and Northumberland, in the northeast of England. It lies partly in the North Pennines Area of Outstanding Natural Beauty and partly in Northumberland National Park. It is said that the best place to see the Whin Sill is High Force, but good views are also available around Housesteads, the site of a Roman auxiliary fort. Formed of dolerite (a basaltic rock) 295 million years ago

Basaltic dyke – Isle of Man

Offa’s Dyke, North Wales

Characteristics & formation of Granite:granite is formed by magmatic intrusion into the earth's crust (forming for example a batholith - e.g. Dartmoor / Isle of Arran) Due to slow cooling, associated with the depth / pressure inside the earth's crust, large crystals of Quartz, Mica and Feldspar form; Granite is a resistant and impermeable rock, but areas with excessive jointing are less resistant and permeable (granite is often characterised by both horizontal and vertical joints) As the granite cooled and contracted, vertical joints formed; Later denudation of the overlying layer of rocks led to pressure release, allow re-expansion of the granite and resulting in the further creation of horizontal and vertical joints. It is these joints that make granite susceptible to weathering processes.http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/communities/Geography/AS%20Geography/AS%20Revision/Earth%20Systems%20Revision/Weathering%20and%20Granite%20Landscapes

Hound Tor, Dartmoor

http://en.wikipedia.org/wiki/Dartmoor Basic geology link

Edinburgh:1. Salisbury Crag - an ancient sill2. Arthur’s Seat - core of the volcano3. Castle Hill - a volcanic plug, once the vent of a parasitic cone

Willow Mountain, on the east side of State Highway 118 three miles north-northeast of Study Butte in southwestern Brewster County and on the way to Terlingua Ghost Town, is a rhyolitic laccolith formed about 40 million years ago in the "aftermath" of the Laramide Orogeny.http://magmacumlaude.blogspot.com/2008_01_01_archive.html

What effects can earthquakes have on

landscapes?

Hanging wall - mass of rocks that lie above the shear plane Normal fault -     Hanging wall goes down in relation to footwall     Crust is lengthened     Rift zones Reverse fault     Hanging wall goes up in relation to shear plane     Crust is shortened     Converging (compression) zones Thrust faults     Very low angle shear plane Oblique normal fault     Rotation movement Lateral (strike-slip) fault     Sliding blocks, sideways movement     Transform plate boundary

Rift Valley, block faulted mountain ranges, basaltic volcanic activity, shallow focus earthquakes

East African Rift Valley     Lake Region     Extends to Jordan River Valley         Sinai Peninsula - Asia and Africa Rift apart         Dead Sea - between Israel/Jordan - 300 m below sea level             Lowest point on continental crust     Djibouti - Red Sea trickles into Africa

*First stage in the development of an ocean basin

Map of East Africa showing some of the historically active volcanoes (red triangles) and the Afar Triangle (shaded, center) — a triple junction where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somali) splitting along the East African Rift Zone (USGS

What do you notice?

What are the advantages and disadvantages of living in this region?

http://geology.com/articles/east-africa-rift.shtml Read this website and explain what is happening in this region of the world and draw a simple sketch diagram to illustrate the key features..

This image shows several fault scarps that are progressively farther away. Essentially we are looking at the edges of several horst blocks from within a graben that contains Lake Baringo

This is an example of a divergent plate boundary (where the plates move away from each other). The Atlantic Ocean was created by this process. The mid-Atlantic Ridge is an area where new sea floor is being created.

As the rift valley expands two continental plates have been constructed from the original one. The molten rock continues to push the crust apart creating new crust as it does.

As the rift valley expands, water collects forming a sea. The Mid-Atlantic Ridge is now 2,000 metres above the adjacent sea floor, which is at a depth of about 6,000 metres below sea level.

The sea floor continues to spread and the plates get bigger and bigger. This process can be seen all over the world and produces about 17 square kilometres of new plate every year.

In the diagram below you can see that the continental crust is beginning to separate creating a diverging plate boundary. When a divergence occurs within a continent it is called rifting. A plume of hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flows and earthquakes would be seen. In the diagram below you can see that the continental crust is beginning to separate creating a diverging plate boundary. When a divergence occurs within a continent it is called rifting. A plume of hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flows and earthquakes would be seen

EarthquakesEarthquake: A vibration of the Earth caused by slippage along a fault.

Hypocentre(focus): The exact location of an earthquake (often far below the surface).

Epicentre: The point on the Earth’s surface directly above the hypocenter.

Foreshocks: Small earthquakes that may precede a major earthquake.

Aftershocks: Earthquakes that commonly occur after a major earthquake, they may be nearly as strong as the initial shock

Seismic WavesEnergy travels away from an earthquake’s focus in waves, both through the Earth and along its surface. Different types of seismic waves include:Surface waves: Seismic waves that travel along the Earth’s surface.Body waves: Seismic waves that travel through the Earth’s interior. There are two types:

Primary waves (P waves): Body waves that compress and expand rock in the direction the waves travel (like a slinky).Secondary waves (S waves): Body waves that shake material at right angles to the direction the waves travel (like shaking a rope). Solid rock transmits S waves, but gases and liquids do not.

FaultsFault: A fracture in the Earth’s crust caused by stress. There are several different types of faults:

Normal fault: A fault in which the hanging wall (the block of crust above the fault) moves down relative to the footwall (the block of crust below the fault) as a result of extension.

Reverse fault: A fault in which the hanging wall moves up relative to the footwall as a result of compression.

Strike-slip fault: A fault in which two blocks of crust slide past each other on the same plane. The San Andreas Fault is a strike-slip fault.

Waterfall formation