Plate Tectonics and Associated Hazards Part Two

So, hopefully you have got through the first part, so onto the second section...of the first part in part two.

Destructive, constructive and conservative plate margins. Processes: seismicity and vulcanicity.

Associated landforms: young fold mountains, rift valleys, ocean ridges, deep sea trenches and island arcs.

Hot spots associated with plumes of magma and their relationship to plate movement, and altitude.

So last time, we looked at the theory of plate tectonics and, off the top of your head name three major plates and three minor plates with their locations. So this time we look at what happens when two or more of these plates hit, slide or dodge past each other. The name of the type of boundary gives the game away:

Plate Margin - a diagram shown here whether they are destructive, constructive or conservative shows three of the plate boundaries - but it doesn't give them the boundary names as given by the AQA board. So take time and three index cards, draw and fully label those plate boundaries. You will need to memorise these to illustrate your exam answer.

Each of these plate boundaries will always have associated process of volcanoes and earthquakes. A good example is along the Mediterranean sea, what type of plate boundary is it and what plates are found there. But what are the associated landforms with their volcanic and seismic activities - the Alps mountain range (see France, Italy, Switzerland and Austria) are young fold mountains caused by two plates rucking or folding up - further proof - Leonardo da Vinci found fossilised sea creatures in the Alps - imagine you playing with your Mother's table cloth - push opposite sides of the cloth together - you get get folds, these are the Alps (to remind yourself of the Alps - think of the A shape of Toblerone, the Himalayas, the Andes, the Rockies - all forms of fold mountains caused by constructive or destructive plate margins. Back to our example of the Mediterranean, there are many volcanoes is Italy and extinct ones in France - one is even mentioned in an advert for bottled French water. There have been recent earthquake in Italy, where the Italian Prime Minister said to the survivors, "It was a bit like camping" as they lived under canvas.

As with examples, make notes on card indexes.

What landforms are associated plate boundaries - write these down on a card index with examples. I have mentioned one above.

Rift Valleys - a large elongated depression with steep walls formed by the downward displacement of a block of the earth's surface between nearly parallel faults or fault systems - eg the one in east Africa (Kenya), the Great Rift Valley.

Ocean Ridges - A mid-ocean ridge is an underwater mountain range, typically having a valley known as a rift running along its spine, formed by plate tectonics - a famous one is found down the middle of the Atlantic ocean.

Deep Sea Trenches - more or less the opposite of the Ocean Ridge - hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor.

Island Arcs or archipelago - an archipelago is a chain or cluster of islands that are formed tectonically.

Hot Spots - apart from the Rock in Cirencester - include the Hawaiian islands in the Pacific ocean - where the TV series Lost was filmed. Just imagine them as zits on a face where they have leaked pus and hardened to form islands. Just don't put that down on your exam.

Vulcanicity

Lava or molten rock is similar to vomit - bear with me on this, it should make you remember, even if it is gross - if you have a lot of gas in your stomach and you try to hold your vomit in whilst running for the loo, the result is normally quite explosive - similar to volcanoes. Lava with a lot of gas or under a lot of pressure will suddenly be very explosive. However if you dribble vomit out of the corner of your mouth whilst you are asleep, you will get a slow and slightly hardening stream of vomit from mouth onto the bed or carpet, wherever you are sleeping. This article explains it with better terminology, which if you use will give you better marks. More material to get rid of, as in a destructive plate margin, will normally lead to higher pressure of molten material to get rid of - hence a more explosive type of lava. There are always execeptions to the rule.

Minor Forms of Extrusive Activity - refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics (hot stones and ash). These include:

Geyser - Not a bloke on Saturday night - A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase (steam). Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma. Generally, surface water works its way down to an average depth of around 2,000 metres (6,600 ft) where it contacts hot rocks. Examples of geysers in Iceland are used for geothermal energy production. Old Faithful in Yellowstone National Park is a famous one and hides a super volcano under it.

Hot Springs - and not Hope springs eternal - A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. Also used in geothermal energy production in Iceland.

Boiling Mud - found near geysers and hot springs and for similar reasons.

Major Forms of Extrusive Activity - unsurprisingly are volcanoes - a good web page that needs reviewing is found here.

As for your case studies - you will need to review your ones from class, make notes on them on your index cards and include who, where, what, why, when and how.