The Unusual Dynamics of the Earth and the Supervolcano Overlapping Mt. St. Helens: Is the Earth Really Really That Deep?
If a person is said to be grounded, it means that they are sensible and stable – solid individuals who can be relied upon to give a careful and considered opinion. The very meaning of the term comes from the solidity and stability of the ground on which we walk. However, recent reports in the media have painted a different picture of what goes on beneath the ground – one in which the core of the Earth is doing some very surprising and unexpected things.
The study shows that the rotation of the core is slowing. The system is still moving at the same speed as the Earth. Furthermore, it appears that the core might be slowing so that it will eventually rotate slightly slower than the Earth. This is interesting, but not as dramatic as some of the headlines have suggested.
The Earth is not a solid ball; it consists of several layers. There is the innermost core, which is a solid sphere about the same size as the planet Mars. Surrounding that is the outer core, which is liquid rock. The next layer is the mantle, which is sort of taffy-like in consistency. Finally there is the crust, which is the outermost layer– the place where we live.
For geologists, this is fascinating stuff. The deepest well anyone has ever dug is 7.5 miles deep, which is shy of 4,000 miles. The continents have a 40 mile deep and thin layer of crust under the oceans. Figuring out the structure of the Earth requires indirect methods, involving studying how fast the waves from earthquakes travel through the Earth, or studying the rich treasure trove of data of how the sound from nuclear blasts pass through the Earth. Nuclear testing stopped with a few exceptions in the 1990s.
Consider the supervolcano that islching above the park. Every half a million years or so (sometimes longer), Yellowstone transforms into a volcano that spews hundreds or thousands times of more ash into the atmosphere than the 1980 eruption of Mt. St. Helens. Recent studies show that there’s no need to worry about the imminent danger of the Yellowstone supervolcano. However, given the magnitude of the damage such an eruption would occur, it is imperative that geologists continue to monitor what is going on.
By understanding the workings of the Earth, scientists can help prepare for the changes that will happen in the magnetic field. If it happened, we’d have to change all instrumentation that relies on compasses to navigate.
And, while a flip is probably not imminent, the location of magnetic north changes even on human time scales. In the early 1900s it was located in the north of Canada, but it moved out into the north ocean and is now approaching Siberia.
Effects of Earth’s innermost core structure on earthquakes based on stacking techniques. II. Observations of the iron crystals
They found that the waves traveled differently through the innermost inner core — which they estimate to be around 650 kilometres thick — than through the outer part. Waves passing through the innermost part of the core slowed down in one direction, whereas waves passing through the outer layer slowed down in another direction. Tkali says the iron crystals are probably organized differently in the inner core than they are in the outer core.
The original earthquakes each reached a magnitude of greater than six, but the waves got progressively weaker as they passed through Earth’s core. The researchers used a technique called ‘stacking’, in which they combined the waveforms from a single event to build a more detailed picture of the distortion from the innermost core.
The study was difficult to achieve and it is important because it gives a measurement of Earth’s innermost section. In order to determine the wave speed in the deep interior of the Earth, you have to amplify the waves that are weak in terms of amplitude.