Friday Headlines, September 27, 2013
THE LATEST IN THE GEOSCIENCES
A new island is born.
Mineral transformations can cause earthquakes.
Paleontologists shouldn’t play Skyrim.
This just in: Water on Mars
On Tuesday, at around 11:30 am local time (7:30 eastern time), a massive 7.7 magnitude earthquake hit south-central Pakistan. According to the United States Geological Survey, this quake occurred along an oblique-strike-slip structure.
The motion occurred where the Eurasia Plate (upon which sits the earthquake epicenter) is affected by the Arabian Plate to the south subducting below it and the India Plate to the east colliding with it.
What’s particularly cool about this earthquake is that the shock caused the creation of a new island off the coast of Pakistan. This new island is the result of a mud volcano. Mud volcanoes are not where molten rock spews to the surface. Instead, mud and sand, carried in water, are pressurized by the shaking, and then spew out forming large, but temporary, islands. This one is about 40 feet high and 200 feet across.
Here’s a video shot last year of a mud volcano eruption.
Most earthquakes occur in the rigid outer layer of the Earth called the lithosphere, which includes the crust upon which we live. These earthquakes are caused when stress due to the motion of continents causes the lithosphere to break and slip along cracks called faults. Most earthquakes occur in the upper 15 kilometers (about nine miles) of the lithosphere.
Some earthquakes occur much deeper in the Earth, sometimes as far as 600 kilometers (about 373 miles) deep, in part of the Earth’s interior that is known to be more plastic and flexible (yet still rock). The causes of such earthquakes have been a bit of a mystery.
On May 24 of this year, an earthquake occurred deep in the earth below the Pacific Ocean. This earthquake had a magnitude of 8.3 on the Richter Scale, but because it was so deep, it was hardly noticed. This quake was four times more powerful than the devastating 1906 San Francisco earthquake.
But since the rock at such great depths is plastic and pliable, faults as we know them on the Earth’s surface do not exist. So what could cause such an earthquake?
All minerals on and within the Earth have certain ranges of temperature and pressure at which they are stable. Outside of these ranges – if it gets cooler, or the pressure decreases – the minerals are unstable and prone to transform into different minerals that are stable under the new conditions of temperature and pressure.
Deep in the Earth, the most common minerals is called olivine. Under conditions of increased pressure and temperature, olivine will spontaneously change its structure to a different mineral called spinel.
This change is essentially instantaneous and results in the creation of fractures in the rock. This rapid change, if occurring in enough olivines at once, can result in a sudden and strong earthquake at great depths, like the earthquake that happened in May.
A sample of soil collected from the surface of Mars has been shown to contain water molecules. If that water could be extracted, there’s about two pints of water for every cubic foot of soil.
That’s a lot of water.
This water isn’t easily accessible. It is bound into the matrix of the minerals and other inorganic compounds that make up the Martian soil.
But it’s there, and that’s a big deal.
Doing a science shows that 1 ton of soil on Mars contains 18 litres of water… so don’t forget to bring a shovel! http://t.co/iVpml2qZKF
— SarcasticRover (@SarcasticRover) September 27, 2013