Research Rack: Did You Know?

• The Earth's plates are in constant, but very, very slow motion. They move at only 1.3 to 10 centimeters per year! This does not seem like much, but over millions of years it adds up to great distances of movement.
• The deepest spot in any ocean is the Mariana Trench. Located at the convergent boundary between the Pacific Plate and the Philippine Plate, this deep-sea trench is 11,033 meters deep. It would take the fastest elevator in the Empire State Building more than 30 minutes to reach the bottom.
• The Earth’s crust varies in thickness from greater than 70 km in some mountainous regions to less than five km thick under the oceanic regions.
• Fossils of Lystrosaurus, a small reptile that lived about 200 million years ago, have been found in South Africa, Antarctica, and India.
• The final bit of evidence in support of sea-floor spreading came with magnetic clues found in the iron-bearing basalt rock in the ocean floor. Changes in magnetic polarity of the rock on both sides of the mid-ocean ridges, reflect the past reversals of Earth’s magnetic poles.
• Eighty percent of earthquakes occur along the edges of the Pacific plate. This ring of seismic and volcanic activity is called the Pacific Ring of Fire.
• On a hilltop in Parkfield, CA lasers monitor the San Andreas Fault as they bounce off a series of 18 reflectors positioned several kilometers away. Any change in a reflector’s position is measured. Movements of less than one millimeter along the fault can be detected.
• There’s an area on Earth, between 105° and 140° from the focus of an earthquake, where no waves are detected. This area is called the shadow zone.
• During the 1985 earthquake, the soft, unconsolidated sediment underlying Mexico City amplified the vibrations of the earthquake.
• Ocean waves generated by earthquakes are called seismic sea waves, or tsunamis. Tsunamis engulf people and entire towns in huge walls of water, causing great destruction and loss of life.
• One of the first steps in earthquake safety is to study the earthquake history of a region.
• The most important thing to remember during an earthquake is to DROP and COVER. Drop and cover means to DROP to the floor and get under something for COVER.