Acid Lava - Thick viscous lava with a high silica content, flows short distances.
Basic lava - Thin, 'runny' lava, low silica content, flows fast for long distances
compressional/destructive plate boundary - two tectonic plates move together
constructive/tensional - where two plates are moving apart
earthquake - a shaking of the earths crust
fold mountains - mountains formed by plate movements
Richter Scale - the scale used to measure the strength of an earthquake.
Tectonic plate - a huge section of the earths crust which moves using convection currents
Volcano - a cone shaped mountain created by lava from repeated eruptions
Compressional / destructive plate boundary
- Plates move together
- the oceanic plate is denser, usually made of granite, and is subducted* below the continental plate.
- The plate melts on the subduction zone where there is heat and pressure
- energy released usually is released as earthquakes and volcanoes
- The rising magma forms composite volcanoes or sometimes fold mountains.
Tensional / Constructive plate boundaries
- where plates move apart
- the gap between the plates is filled with magma
- magma rises to form shield volcanoes
- they form sub-marine volcanoes and volcanic islands
-fold mountains form when rivers containing sediment flow into a geosyncline in the earth
-as more and more sediment settles on the bottom the weight of it compresses it into sedimentary rock such as sandstone.
-Plates on either side of the geosyncline at a destructive plate boundary push in folding the sedimentary rock up
-the peaks formed are called synclines and the dips are called anti-synclines.
-an example of a fold mountain range is the Alps.
Human Activities in the Alps
-mostly on the valley floor where it is flatter, more sheltered,warmer, with deeper more fertile soil.
-Traditionally dairy farming. or sheep hearding as they can live high up in the mountains
-Main crops are hay and cereals with some wines or fruit in warmer areas.
-use upland pastures in the summer.
HEP and Industry
Industry needing large amounts of electricity, e.g, sawmills, smelters need to locate near HEP stations which generate cheap electricity from fast flowing rivers
Traditional Industries include Paper and Furniture making
Human Activities in the Alps continued...
Conifers cover the slopes up to about 1800 meters. The wood is used for fuel, building chalets and for paper making.
Tourists are attracted by;
-Winter Resorts e.g chamonix
- summer resorts e.g lakes
-Winter Sports e.g skiing
-Good scenery and alpine climate
-ease of access through good communications
Composite cone volcano
They are tall volcanoes formed at destructive plate boundaries.
They are tall compared to their width
they are composed of alternate layers of ash and lava
they sometimes have subsidiary cones as well as the main vent.
their lava is acidic
they have gentle slopes with a wide base and a relatively low height
Frequent, usually non-violent, eruptions of basic lava
lava flows more easily, travels longer distances before cooling
Volcano case study : Montserrat,
-A british colony in caribbean
-population 12,000, half in the capital plymouth
Eruption of long dormant volcano soufrire hills, first time in 350 years. in July 1995
deadly pyroclastic flow flows down the side of the mountain.
50% of the population evacuated to the north of the island in first month and the other half evacuated the island all together.
plymouth, the capital city became a ghost town covered in ash destroying homes and causing forrest fires as the trees burnt up in the lava.
industry, particularly farming due to destroying of farmland, crippled. Also the tourist industry greatly suffered as nobody wanted to go to an island with a massive ash cloud above
Volcano case study : Montserrat continued...
evacuation of over 5000 people abroad particularly Britian
many people moevd north of the island and made makeshift refugee camps
riots cooured as locals felt the british government wasn't doing enough to help
£41 million given in aid in total
£2400 given to each resident, they demanded £20,000
temporary shelters provided
Earthquakes are vibrations in the earths crust, usually along plate boundaries. they occur when pressure builds up behind a certain point and when the pressure is suddenly released it releases seismic waves which vibrate the earth which can cause earthquakes.
Earthquakes are measured on the richter scale which is a logarithmic scale, goes up in powers of 10 for every increase. it is measured using a seismograph.
the focus of the earthquake is the area in the earths crust where the earthquake occured
the epicenter of an earthquake is the point directly above the focus on top of the crust
Comparing two earthquake case studies in MEDC's an
San francisco 1989 (MEDC)
the epicenter was in the santa cruz mountains a few miles away.
it happened 5:04 PM 17 october 1989, same day as the super-bowl (many people were out)
the earthquake measured 7.0 on the richter scale
63 dead with 13,000 homeless
liquefaction occurred under-ground in some areas sinking buildings
house-fires spread quickly from house to house
freeway collapsed crushing many cars beneath as well as bridges collapsing
gas/water/sewage/electricity pipes ruptured leaving people without services
$7 billion damaged caused
Comparing two earthquake case studies in MEDC's an
Bam 2003 (LEDC)
5:26 AM december 26 (everyone was asleep in bed)
the earthquake had a magnitued of 6.7
the epicenter was right next to the town
43,000 dead with over 70% of all buildings flattened crushing thousands as the houses were made out of mud bricks and so collapsed easily
The hospitals were destroyed which meant it was difficult to treat the injured
disease spread quickly around the makeshift tens which were erected to temporarily hold the homeless.
$1 billion given in aid from the UN