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"Continental Drift Pangea Final" Pangea Plate Tectonics (english version)

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Volcanoes form when magmas make their way to the Earth's surface and erupt. Volcanoes vary by type; cinder cones, stratovolcanoes or shield volcanos. The intensity of the eruption depends in part on the composition if the lava, and following, how much gas is contained within the melt and how viscous (reseitive to flow) the magma is upon reaching the Earth's surface.

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Weathering

Weathering is the breakdown of rocks at the Earth's surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rock material.

There are three types of weathering, physical, chemical and biological.

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Weathering Weathering is the breakdown of rocks at the Earth's surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rock material. There are three types of weathering, physical, chemical and biological.

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Liquefaction is a process that temporarily turns firm ground into a liquid. During the Canterbury earthquakes of September 2010 and February 2011, liquefaction caused silt and fine sand to boil up and bury streets and gardens and caused buildings and vehicles to sink. This was a new phenomenon for most New Zealanders, yet it has been a feature during earthquakes throughout this country's history. There is evidence of liquefaction in most of the largest earthquakes since the 1840s, including the Hawke's Bay quake of 1931.

Next time you are on a sandy beach, walk across some wet sand a little back from the water's edge. It's firm walking, though you might leave footprints. Now stand still, wriggle your toes and feet. If conditions are right, you could sink a little as the sand around your feet becomes sloppy. This is similar to what happens during liquefaction.

Causes of liquefaction

Over thousands of years, rivers deposit layers of silt and sand in many places, especially in low-lying ground and near the coast. The top layer of sediment can become flat, firm and dry - ideal for building on - but this often hides layers of waterlogged sediment beneath.

Severe shaking in an earthquake puts pressure on the silt and water particles in these waterlogged layers, turning once firm sediment into a liquid. Pressure on the liquefied layer is increased by the ground above it pushing down. Water fountains and sand boils can burst upwards through any cracks.

It's a bit like using a coffee plunger carelessly. If you push the plunger down too quickly, the water and coffee grounds are put under pressure. If they find a gap around the edge of the plunger they spray up all over the bench or table.

Damage from liquefaction

Liquefaction only happens when underlying waterlogged silts are present and when shaking is severe. When the ground becomes liquid, it can no longer support the weight of buildings, so these tend to sink. The overlying ground can also sink, spread and crack. Underground pipes and tanks float and break. Power poles fall and break cables. During the 2010 and 2011 Canterbury earthquakes, over 400 000 tonnes of silt came to the surface, covering streets and gardens in several suburbs.

Liquefaction is not just a New Zealand problem. In 1995, the Japanese city of Kobe suffered extensive damage from an earthquake. The port had been built on artificial islands made of relatively loose sand and silt, and many buildings collapsed during the liquefaction that happened here.

Reducing liquefaction hazards

The Museum of New Zealand Te Papa Tongarewa is on the waterfront in Wellington. The ground was considered to be at risk from liquefaction in the event of an earthquake, so it was compacted before building started. This involved dropping 30-tonne weights on the ground over 50 000 times, which took several months. Together with base isolators, this gives Te Papa considerable protection during an earthquake. Ground compaction also worked to reduce liquefaction damage in some residential areas of Christchurch during the 2010 and 2011 earthquakes.

Another way to reduce damage in areas at risk from liquefaction is to place buildings on concrete pillars that go through the sediment layers to firmer layers beneath. If the liquefaction-prone layers are shallow enough, they can be dug out and replaced with a firmer fill.

Nature of science

Useful links

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Liquefaction is a process that temporarily turns firm ground into a liquid. During the Canterbury earthquakes of September 2010 and February 2011, liquefaction caused silt and fine sand to boil up and bury streets and gardens and caused buildings and vehicles to sink.

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Soil Type and Shaking Hazard in the San Francisco Bay Area

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USGS Earthquake Hazards Program, responsible for monitoring, reporting, and researching earthquakes and earthquake hazards

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A quick and fun cartoon lesson about volcanoes. Great for teachers and students- hope you guys enjoy! Be sure to subscribe if you like it, there will be more soon.

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This video shows the difference between bedrock/ consolidated sediment (the rice crispy treat) and unconsolidated sediment (the jello) during an earthquake.

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Hot Chocolate Mantle Convection Demonstration

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This episode discusses the scientific theory of plate tectonics, in which the Earth's crust is subdivided into a series of large and small tectonic plates. Convergent, divergent or transform boundaries are discussed and demonstrated with brittle graham crackers and icing to illustrate the motions of the plates at these boundaries.

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How Earthquakes Trigger Tsunamis - Bang Goes The Theory, Preview - BBC One

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http://www.bbc.co.uk/bang Follow Bang on Twitter @bbcbang and #bbcbang. Jem Stansfield explains how pent-up energy between tectonic plates can cause a tsunami when it is eventually released.

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Watch more How to Do Fun Tech & Science Projects videos: http://www.howcast.com/videos/262265-How-to-Build-an-Erupting-Volcano Have fun and make a mess, all in the name of science. Step 1: Make clay Make homemade clay by mixing the flour and salt in a bowl, and then adding water until the mixture is smooth in consistency.

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The Earth is an active planet. Earthquakes shake and volcanoes erupt. Sections of the crust are on the move. Mountains push up and wear down. These and many other processes contribute to the rock cycle, which makes and changes rocks on or below the Earth's surface. The Earth is 4.6 billion years old, but you won't find rocks that old because they have been recycled into younger rocks.

Rocks are made of minerals, which are made of specific chemical elements. For example, the mineral quartz is made of the elements silicon and oxygen. The rock called granite consists mostly of the minerals quartz, feldspar and mica.

There are three main types of rock - igneoussedimentary and metamorphic.

Igneous rocks

Magma is a hot mix of melted minerals, and igneous rocks are formed when it cools. Cooling can happen quickly above ground to form volcanic rocks such as basaltrhyolite and andesite. Cooling can also happen slowly below the surface to form what are called plutonic rocks, such as granite.

Sedimentary rocks

On the surface of the Earth, the processes of weathering and erosion can break down any rock into small pieces called sediments. These sediments are carried away by water or wind and dumped somewhere else. The pebbles, sand and mud you find at the beach are sediments from broken down rock, transported there from somewhere else. Over a very long time, layers of sediment build up at the bottom of seas and lakes, squeezing water out of the layers beneath. Chemicals then cement the sediments into sedimentary rocks such as sandstone and mudstone. The remains of dead animals and plants often get trapped in sediments and can get turned into fossils by the same processes that turn sediments into rock.

Not all sedimentary rocks are made from broken pieces of other rocks. For example, limestone can be formed from the build-up of dead marine organisms on the sea floor or by chemical processes causing minerals to precipitate out of water.

Metamorphic rocks

The Earth's crust is constantly, but slowly, on the move. Enormous forces push up, tilt, fold and break rocks. These processes can heat and squeeze any type of rock enough to change their structures. Such changes are called metamorphoses, and the resulting rocks are called metamorphic rocks. Marble is an example of a metamorphic rock - it is squashed and heated limestone. You may have come across the word metamorphosis before, because it is used to describe other types of change, such as a caterpillar changing into a pupa and then a butterfly.

There are parts of the Earth, called subduction zones, where the crust is carried deep inside. There is a subduction zone beneath the North Island of New Zealand. Deep down, any type of rock can melt into magma, which later cools to form igneous rock, continuing the rock cycle.

Interacting cycles

As part of the rock cycle, any rock can be changed into one of the other rock types or into a different form of themselves. For example, sedimentary rock can be broken down to form new sedimentary rock, or it may be changed into metamorphic rock. Material does not always go round in a neat sequence, but takes part in a whole network of processes.

The rock cycle interacts with other Earth cycles in many ways. For example, rivers of the water cycle transport sediments, and seas and lakes are where these sediments are dumped. Many sedimentary rocks formed beneath the ocean trap carbon as part of the carbon cycle.

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The Earth is an active planet. Earthquakes shake and volcanoes erupt. Sections of the crust are on the move. Mountains push up and wear down. These and many other processes contribute to the rock cycle, which makes and changes rocks on or below the Earth's surface.