Scientists record key event that breaks continents apart

December 10th, 2008 - 4:58 pm ICT by ANI  

Washington, Dec 10 (ANI): An international research team has captured for the first time a geological event considered key in shaping the Earths landscape, by breaking apart the continents.

The team, led by Eric Calais, a Purdue University professor of geophysics, was able to measure ground displacements as two tectonic plates in Africa moved apart and molten rock pushed its way toward the surface during the first so-called dyking event ever recorded within the planets continental crust.

The event left a wall of magma 6 miles long and 5 feet wide wedged between the two plates.

Dyking events have been reported in the thin oceanic crust, but had never been directly observed and quantified in the thicker areas of the planets shell, according to Calais.

Such dyking events had been included in theories, but researchers had never before been in the right place at the right time with the right equipment to record them, Calais said.

According to Calais, the event was preceded by a slow slipping of the tectonic plates along a fault line. This also had not been seen before.
Faults usually slip suddenly, which produces earthquakes, but this was a very seismically quiet course of events that lasted about one week, he said.

The existence of these events provides a key element of how the Earths rigid outer shell - the lithosphere - breaks apart and moves.

The known forces pushing and pulling on continents are not powerful enough to break them apart.

However, repeated dyking events could weaken the lithosphere severalfold, allowing it to shift and break under far less force, Calais determined.

To break a continent apart, one needs to overcome the strength of the Earths lithosphere, he said.

But, when we calculate the forces available from plate tectonics, we find that they are not large enough to do the job. We know that continents break apart and have done so repeatedly in the geological past. So, how can it happen? One way is to add a little push to the system, and this is exactly what dyke intrusions do, he explained.

During a dyke intrusion, magma held in deep reservoirs breaks through surrounding rock and rises toward the surface, forcing the two plates apart, and, over time, weakening the lithosphere by transferring heat to the surrounding rocks.

The magma fills and widens cracks and fractures as it rises. The end result is a vertical wall, or dyke, of magma that has pushed the Earths crust apart. (ANI)

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