Layers of the earth, plates, faults, tectonic landscapes, convergent, divergent plate margins, fold mountains
Volcanoes - types, dangers of volcanic eruptions, advantages of volcanic activity, primary, secondary effects, Mount Merapi Indonesia
Earthquakes - effects, responses, living in an earthquake zone,
click image to access quick revision of tectonic plates and continental movement
The Pacific Plate (on the west) moves northwestward relative to the North American Plate (on the east)these moving plates meet in western California; the boundary between them is the San Andreas fault, causing earthquakes along the fault. The San Andreas is the "master" fault of an intricate fault network that cuts through rocks of the California coastal region. The entire San Andreas fault system is more than 800 miles long and extends to depths of at least 10 miles within the Earth.
The presence of the San Andreas fault was brought dramatically to world attention on April 18, 1906, when sudden displacement along the fault produced the great San Francisco earthquake and fire. Read more from the USGS webpage HERE
An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter. Read MORE
What factors determine the destructiveness of an earthquake?
Location, Magnitude, Depth, distance from epicenter, Geologic condition, secondary effects, architecture. Read more details from the Smithsonian blog
Economic development of the location
Urban or rural area
Distance from epicentre
Weather and season
Time of day and Day of week
Emergency services and earthquake response plans
Landscape and rock type
• Shaking: moves the ground in place. This does not usually cause significant damage to the ground itself, but often results in major damage to structures in or on the ground. This can include, not only buildings, but water, gas and sewer lines, train tracks, and roads.
• Landslides: ground is moved (displaced) to somewhere else .
• Liquefaction: strength of the ground is removed, causing the ground and objects on it to sink. Any heavy objects sitting on liquefied ground will rapidly sink. This includes all types of natural features as well as structures. Liquefaction can result in depressions, a type of landslide called a lateral spread, and the formation of sand blows
PORT-AU-PRINCE v CANTERBURY
Wealth: NZ much better resourced to cope.
Building codes/standards: Haiti's lacking.
Ground motion: Significantly less in Christchurch due to faulting distance.
Readiness: NZ's history of earthquakes meant Cantabrians knew what to do.
Emergency response: The comparatively minimal damage meant services could respond quickly, hospitals stay open.
Luck: The Christchurch quake struck at night when people were asleep, businesses shut.
There are three main types of plate boundary: divergent, convergent and transform. Plates move away from one another at divergent boundaries. This happens at mid-ocean ridges.
Plates move past on another at transform boundaries. The most famous example of this type of boundary is the San Andreas Fault in California. Read more about this from BBC
There are a few handfuls of major plates and dozens of smaller, or minor, plates.
Six of the majors are named for the continents embedded within them, such as the North American, African, and Antarctic plates. Though smaller in size, the minors are no less important when it comes to shaping the Earth.
The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States. Read more from NatGeo
Magnitude is a measure of the energy released during an earthquake, and it's related to the size of its waves on a seismogram. Seismologists use several different magnitude scales to desribe the size of a quake. The Richter scale is the one most commonly referred to. For mathematical reasons, Richter is accurate only up to about 6.5. For larger quakes, scientists use the newer moment magnitude scale. source
How do scientists measure jolts such as the recent disaster in Japan? Hint: They don’t use the Richter scale.
At first blush, the earthquake that struck Christchurch, New Zealand on Saturday was the spitting image of the one that ravaged Haiti in January. Each was a powerful magnitude 7.0 quake, and each occurred on a strike-slip fault near a major population center.
Reports out of Christchurch have been almost miraculous: Though the city suffered extensive damage, not a single person out of nearly 400,000 appears to have died. By contrast, the Haitian capital city of Port-au-Prince was flattened, and a quarter of a million people were killed.
What are the reasons for such a stark contrast ? Read from these two news articles to find out
Volcano - a vent (opening) at the Earth's crust through which magma (molten rock) and associated gases erupt.
Magma - molten rock beneath the surface of the Earth.
Lava - magma that has reached the surface.
Cinders - lava fragments about 1 centimeter in diameter.
Pyroclastics (“fire fragments”) - ash, cinders, angular blocks, and rounded bombs (block and bomb fragments can be over 1 meter in diameter).
Explosive eruptions – eject lava and pyroclastics.
Quiet eruptions – fluid lava flows out of a volcano's vent.
Click on image to read about Volcano types from Utah geological survey
Volcanic eruptions are one of Earth's most dramatic and violent agents of change. Not only can powerful explosive eruptions drastically alter land and water for tens of kilometers around a volcano, but tiny liquid droplets of sulfuric acid erupted into the stratosphere can change our planet's climate temporarily.
click on image to read full details