Friday Headlines, March 13, 2015
THE LATEST IN THE GEOSCIENCES
The age of sponges.
How did the high plains get so high?
Happy birthday little island!
600 million years ago.
Sponges are animals. That little bit of knowledge is a bit surprising to most, considering that most sponges we ever see are busy sitting on the bottom of the ocean, seemingly doing nothing. Sponges do have this amazing ability to regenerate themselves from isolated – something not seen in any ‘higher’ or ‘more advanced’ animal.
So understanding sponges can help us understand modern ‘advanced’ life like ourselves. How did we go from isolated cells to colonies with skeletons (like sponges)? How did we get from simple colonies to large, complex organisms like ourselves?
This new find places the origins of sponges at at least 600 million years ago. Knowing this helps us know when the crucial split between independent forms and colonial forms happened, and can shed light on the advent of the more complex forms leading to us.
70 million years ago.
Continents ‘float.’ They sit atop denser asthenosphere below and float and move along much like icebergs with a long root that’s invisible beneath the surface. The density of the continent determines how high it will float. If you consider wood floating in water, dense pine will float lower than will float balsa wood.
When there are large, high-altitude regions on Earth, this raises questions about why the continent is floating so high right there. There is plenty of research underway to explain both the Tibetan Plateau of Asia and the Altiplano of South America. The western part of North America, the so-called ‘high plains’ are also of curiously high altitude. Consider Denver, the mile-high city. The Rocky Mountains themselves provide some explanation for the high altitude, but aren’t sufficient.
New research suggests that chemical reactions deep in the crust have caused the crust of the high plains to be less dense, and thus float higher, resulting in the high elevation. The suggested reactions involve the alteration of dense garnets deep in the crust to less-dense minerals by the addition of water.
So how do you get water hundreds of kilometers down? It may have been transported there with ancient ocean beds that were subducted beneath North America when the west coast was a massive subduction zone (subduction still occurs along the Cascade Range, the Aleutian Islands, and in Mexico). Water from the ocean was incorporated in sediments that were dragged under the continent, then later released because of high temperatures and pressures. This water then reacted with the garnets, decreasing the density of the lower crust, and caused the high plains to rise.
Or so scientists hypothesize.
It’s an interesting and plausible idea. Only more research can prove or disprove it.
Just a few months ago.
A new island broke the ocean’s surface in January if the coast of Tonga. It’s currently about 800 meters in length. There’s no telling if it will last or it will sink back into the sea when eruptions stop. But for now, it’s simply beautiful. You could go an look at the photos. Seriously.