Naturally Speaking

A Dynamic Planet, part one

Community Contributed by G.T. Larson

The world has been shocked by the disaster in Japan caused by the earthquake and accompanying tsunami. We have been mesmerized by the videos and photos of the actual tsunami and its impact, literally and figuratively. We also now have experienced the magnitude of an event approximately 3,800 miles away. Along with our sympathy, prayers, and financial support, we in Hawaii would do well to have at least a basic understanding of the geological events that caused this tragedy.

If humans did not live on this planet – or in critical areas, such as the Pacific Basin – then earthquakes and their sometimes associated tsunamis would be amazing examples of the ongoing dynamics of our planet. When an earthquake strikes, the earth literally moves under our feet, violently. However, in reality the earth is constantly moving under our feet, just so slowly that we do not notice it, for we are gently being carried along with it.

The earth’s surface is a mosaic of irregular shaped puzzle pieces, called plates, which are constantly moving either toward, beside, or away from each other. This causes a range of geologic events, not unlike the way we make puzzle pieces fit together through the application of force. This is called plate tectonics.

There are three main types of plates: convergent, divergent, and transform.
Convergent plates are plates that are converging or coming together. When these plates are land masses, such as the Indian and Asian plates, then they crumple up as would two pieces of paper slid together on a table top. This coming together, as it were, is the ongoing formation of the Himalayan mountain range. When an oceanic plate meets a landmass, the landmass wins and the oceanic plate submits or more properly, sub ducts, along what is called a subduction zone.

A divergent plate is where two plates are diverging or moving away from each other. The mid-Atlantic ridge is a fine example of several plates moving apart. The North American and South American plates are separating from the Eurasian and African plates at the mid-Atlantic ridge.

Transform plates are where two plates are sliding or grinding past each other. The San Andreas Fault is a well-known example of a transform fault, where a section of the North American plate is sliding against the Pacific plate.

In our next installment, we will more closely examine the mechanics that resulted in the earthquake in Japan in particular, and how these mechanics affects the Pacific plate in general, for this is the piece of the Earth’s puzzle that we are riding on. Aloha Ke Akua.

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