Divergent Plate Boundaries
Divergent plate boundaries are where new oceanic lithosphere (crust) is born. The most prominent feature on planet Earth is the mid-ocean ridge system even though we can't see it in its entirety. It is, in fact one long divergent boundary that includes the Mid-Atlantic Ridge system, the Pacific Rise system, and many others that spread out around the globe making up one large continuous system.
The system as a whole stretches over 70,000 kilometers long, and is usually 2-3 kilometers taller than the surrounding sea floor. As part of the mantle that is partially melted pushes up from below, it forces the neighboring plates to move away from each other. As the lava cools it creates new lithosphere and drives a process called seafloor spreading. This occurs at different rates affecting the ridge features and profile at these sites. Below is a profile of the Mid- Atlantic Ridge, where the North American plate and the Eurasian plate are moving away from each other. Notice the high ridge, which is due to the hotter lighter oceanic crust having more volume thus making it less dense and more buoyant .
Notice all of the seismic activity that occurs along the ridge. This is represented by all the orange spots running along the red line which indicates the divergent boundary ( the ridge). The earthquakes that occur here tend to be shallow and average a magnitude of around 5.6, a moderate earthquake. They occur rather frequently. This is a result of the tensional forces pulling the plates apart at the divergent boundary.
The following is a profile of the East Pacific Rise. This divergent boundary is located in the Southeastern Pacific, west of South America. The volcano icon represents Easter island. This divergent boundary has a faster spreading rate compared to the mid Atlantic ridge. This gives its profile a slightly different topography, with a more shallow slope.
Again notice the distribution of earthquakes along the red line (the divergent boundary) and along the blue lines (transform boundary) . The orange dots at the top show the depth of the earthquake as represented by the key on the left. Again these are shallow, moderate earthquakes that are around a 6.0 magnitude.
A very unique feature located at divergent boundaries are hydro-thermal vents. These "black smokers" as they are sometimes called, spew super heated water. These waters are up to 400 degrees centigrade, yet do not boil due to the extreme pressure. The water is also rich with minerals which leave behind large structures that are home to a very unique ecosystem found nowhere else on Earth. These are the images to the right.
|
|
Below is a unique feature located at the divergent boundary between the North American and Eurasia plates. A hot spot is located directly on the Mid-Atlantic ridge pumping out continental lithosphere, thus creating the Island of Iceland. Here is a place where we can see a divergent boundary on dry land. You can learn about hot spots by clicking here.
Here is another beautiful landscape as a result from this unique location. On one side you have the North American Plate, and on the other the Eurasian Plate.
Follow this link to see some useful information we can collect from studying the effects of sea floor spreading as a result of divergent plate boundary's.