Is your life affected by plate tectonics?

Plate Tectonics

The Earth's surface is not fixed, solid though it may seem to most of us most of the time. The top layer of the Earth's crust plus the top of the mantle, down to about 100km (known as the lithosphere), is divided into a number of lithospheric plates, as shown in the map below. The theory of how these plates behave is called Plate Tectonics.

Map courtesy of NASA's Observatorium

USGS map

The plates have been on the move for a very long time; in the Triassic period around 200 to 240 Ma (million years) ago most of them formed a large continent called Pangaea. Pangaea split into several smaller plates which split apart and moved around the Earth, but it is still possible to see how the eastern side of South America and the western side of Africa fit, for example.

Currently, some of the plates are bumping up against each other, others are splitting apart from each other, and yet others are sliding past each other. Where they are bumping up against each other and one is a continent and the other is under the sea, the sea one is subducted under the continental one, and a deep sea trench is formed as well as volcanoes. Where two plates are pulling apart, in mid ocean, molten rock rises up and forms new land in a process called sea floor spreading. The friction when two plates move sideways past each other results in earthquakes such as the one that caused a tsunami on December 26 2004. Tsunamis are comparatively rare however, depending on where the earthquake takes place and whether there sis enough vertical movement to move a large mass of water.

The boundary of the Pacific plate is called the "Ring of Fire" and includes New Zealand and over 75% of the world's active and dormant volcanoes. There are also some "hot spots", such as Hawaii or Yellowstone. These volcanoes are believed to form on the land as it passes over a huge column of upwelling lava, or "plume" under the plate. The active volcanoes of Hawaii are over one such plume now, and there is a chain of older islands stretching all the way to Kamchatka, north of Japan. The Galapagos Islands, the Easter Islands, and the Pitcairn Islands all originated from hot spots.

Further links: Plate Tectonics and Sea-Floor Spreading, Subduction Zones, "Hot Spots", and the "Ring of Fire" (USGS).

The world is a very restless place. Scarcely a week goes past without news of fairly major earthquakes or eruptions. Occasionally there is news of a tsunami too. These topics will be covered on other days, but for example, here are some recent news stories involving volcanoes:

• Hawaii's Kilauea Volcano a Big Polluter May 17 2005
• Mount Rainier 3rd Most Dangerous Volcano May 17 2005
• Krakatoa volcano sparks tsunami panic in Indonesia May 16 2005
• Volcano Fernandina erupts in Galapagos Islands May 13 2005
• Yellowstone Rated High for Eruption Threat May 06 2005
• US geologists press for volcano early warning plan May 02 2005
• Report Urges Increased Volcano Monitoring April 29 2005
• Alaska's Mount Spurr Continues to Rumble April 20 2005
• Volcano Erupts April 19 2005
• Comoros Volcano Victims Return to Dirty Water April 19 2005
• Thousands Flee Comoros Volcanic Eruption April 18 2005
• Indonesia Scientists Monitor 3 Volcanoes April 14 2005
• Activity Changes Dome of Mount St. Helens April 13 2005
• Indonesian Volcano Prompts Evacuation April 13 2005
• Volcano on Indonesia's Sumatra Erupts April 11 2005
• Scientists: Yellowstone Eruption Unlikely April 08 2005
• Saipan Volcano Erupts Over Pacific Islands April 06 2005
• 8.7 Quake Hits Indonesia March 28 2005
• Mexico's Volcano of Fire Spews Hot Lava March 11 2005
• Restless Volcano Creates Hazards in Alaska March 04 2005

Please see the following message for the remaining stories.

Amazon Deforestation Up 6 Percent in 2004

Over 10,000 square miles of Amazon rain forest was destroyed in 2004, the second worst year. The forest was cleared for logging, ranching and soybean farming. Environmentalists are disappointed that the government had not succeeded in its aim of reducing the rate of destruction. As much as 20 percent of the forest, which is considered to be the world's "lung" (trees produce oxygen and absorb carbon dioxide), has now been destroyed.

Antarctica scientists get big ice cube delivery

Iceberg B15G, part of the massive iceberg B15 which broke off from the Ross Ice Shelf 5 years ago, has entered Vincennes Bay, off Australia's Casey station on the south east coast of Antarctica and come to a halt. Wildlife is not believed to be affected.

Tropical Storm Threatens Central America

The season's first tropical storm, Adrian, is headed for Central America. Boats have been warned to return to port.

Flood Washes Out Road to Airport in Alaska

The Yukon River has overflowed and washed out the road from Emmonak to its airport, so that freight cannot be brought in. There has been a lot of flooding in Alaska this year as a lot of ice has broken up and created ice dams and high water.

Bird flu virus mutating, posing bigger threat-WHO

The WHO believes that the H5N1 human bird flu virus may be mutating into a form that transmits more readily between humans, If true, this would make it more likely to lead to a pandemic.

Marburg fever death toll tops 300 in Angola--WHO

The World Health Organization (WHO) says there have been 337 cases since late last year and 311 have died. The situation is getting better due to education. The outbreak is not yet over, however.

Tons of Debris Bagged in Coastal Cleanup

A massive volunteer cleanup of many of the world's beaches bagged a huge tonnage of rubbish, with cigarettes and food wrappers being the most common articles found, according to The Ocean Conservancy. There were some surprising finds.

Feds to Restrict Off-Road Vehicles in West

The United States' Forest Service and Bureau of Land Management are planning to restrict off-road vehicle travel in order to prevent further environmental damage and disturbance to other users of the land.

Judge Denies Tribal Plea to Halt Nuke Dump

A federal judge ruled against an Indian tribe who wanted to block plans for the proposed Yucca Mountain nuclear repository in Nevada.

UK firm claims breakthrough in fuel cell technology

A small British company claims to have designed a new fuel cell only one tenth the size of existing designs, capable of powering laptop computers for four times as long as conventional batteries. The fuel cell would be instantly rechargeable and would run on methanol initially, and would produce very little carbon dioxide, which is a greenhouse gas.

Newfangled Forecasting Enrages Britons

The British Broadcasting Corporation has run into protests about its new 3D "virtual reality" graphics weather reports on TV. Your intrepid reporter switched on the television for the weather report to check. Complaints included:

• Scotland and the islands beyond looked too small (this is caused by foreshortening, as the main viewpoint is from somewhere south and west of England, and from high enough to see the curvature of the Earth)
• the land is shown as a drab brown rather than a pleasant green
• there are no isobars, fronts, or other indicators of wind speed and direction.

People miss the sight of a nice bright sun, or even fluffy clouds.

Is your life affected by plate tectonics?

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