The next step is continental drift, sea-floor spreading, ocean formation — and hello, Atlantic Ocean.
In fact, the Atlantic is still opening, generating new plate material in the middle of the ocean and making the flight from New York to London a few inches longer each year. Oceans close when their tectonic plate sinks beneath another, a process geologists call subduction. Off the Pacific Northwest coast of the United States, the ocean is slipping under the continent and into the mantle below the lithosphere, creating in slow motion Mount St Helens and the Cascade mountain range.
In addition to undergoing spreading construction and subduction destruction , plates can simply rub up against each other - usually generating large earthquakes. But the conventional theory of plate tectonics stumbles when it tries to explain some things. For example, what produces mountain ranges and earthquakes that occur within continental interiors, far from plate boundaries?
The answer may lie in a map of ancient continental collisions my colleagues and I assembled. Globally, we find many instances of scarring left over from the ancient collisions of continents that formed our present-day continental interiors.
What drives plate tectonics? | EurekAlert! Science News
A map of ancient continental collisions may represent regions of hidden tectonic activity. If these deep scarred structures more than 30 km down were reactivated, they would cause devastating new tectonic activity. It looks like previous plate boundaries of which there are many may never really disappear. These inherited structures contribute to geological evolution , and may be why we see geological activity within current continental interiors.
These hot, dense piles of material lie beneath Africa and the Pacific. And nobody knows where they came from or what they do.
When these blobs of anomalous substance interact with cold ocean floor that has subducted from the surface down to the deep mantle, they generate hot plumes of mantle and blob material that cause super-volcanoes at the surface. Does this mean plate tectonic processes control how these piles behave? Or is it that the deep blobs of the unknown are actually controlling what we see at the surface, by releasing hot material to break apart continents?
Answers to these questions have the potential to shake the very foundations of plate tectonics. Plate tectonics then may not be the same as what our conventional theory dictates today. The earthquake occurred on a previously unmapped fault and continued along the Denali fault. Surface offsets of up to 29 feet 10 meters were observed.
Evidence for the theory
Projects such as the PBO are important because they provide more precise maps of unnamed faults and information about the hazards associated with them. The graphs above show the value of having a long-term GPS station at a site.
Even if the station moves only a fraction of an inch or of a centimeter per year, as the small movements in these three dimensions accumulate over years, the trending or long-term movements of the Earth—from faults or plate tectonic activity—can be detected. The top graph shows that the WIKR station has moved to the south north dimension has decreased about 0.
The second graph shows a descending trend line, indicating that the east component is less, or that the station is moving slightly westward. The station also is showing a very slight downward motion third graph is decreasing in the height component. Where the time series graphs show breaks in data, or show lots of seasonal variation in motion, snow and ice loading may have influenced the readings. When years of this kind of data have been collected and analyzed, scientists can model where tectonic forces are building up places with earthquake potential and infer other information about plate motion and local crustal dynamics.
Through many partnerships—including with the U. The goal is to improve knowledge of earthquake processes and volcano behavior, in order to better assess natural hazard risk near the boundary of these two tectonic plates.
Modern plate tectonics arose 3.2 billion years ago
Download a printer-friendly version of this article. Explore This Park. Studying the Active Boundary of Tectonic Plates. Earth's surface is a very active place; its plates are forever jiggling around, rearranging themselves into new configurations. Continents collide and mountains arise, oceans slide beneath continents and volcanoes spew. As far as we know Earth's restless surface is unique to the planets in our solar system.
So what is it that keeps Earth's plates oiled and on the move? Scientists think that the secret lies beneath the crust, in the slippery asthenosphere. In order for the mantle to convect and the plates to slide they require a lubricated layer.
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On Mars this lubrication has long since dried up, but on Earth the plates can still glide around with ease. Beneath continents the asthenosphere appears at around km depth, while under oceans it can be as shallow as 60km. Above the asthenosphere lies the lithosphere: a more rigid layer that includes the crust.
By km depth the asthenosphere comes to an end and the mantle goes back to a less flexible state. What makes the asthenosphere so slippery and why does it exist on Earth but not other planets?
These are some of the key questions that have puzzled Earth scientists ever since plate tectonics was discovered, but only now are the answers starting to emerge. A combination of new experimental techniques and powerful computational theory is enabling scientists to work their way through the asthenosphere atom by atom. This water is no longer in its liquid state, but is bound to oxygen in crystal structures to form hydroxyl OH- groups instead.
The question that really interests Winkler is 'where does the water go'? Which minerals are clinging on to their hydrogen and enabling the Earth to perform its plate tectonic dance? Unfortunately we can't get samples from the asthenosphere -- no-one has ever managed to drill a hole deep enough.
But seismic wave patterns and magma spurting out of volcanoes give us clues as to which minerals make up the majority of the asthenosphere. Winkler finds samples of these candidate minerals on the Earth's surface and, using specialist experimental equipment, subjects them to the pressures and temperatures estimated for the asthenosphere.