Friday Headlines, October 3, 2014
THE LATEST IN THE GEOSCIENCES
Pegmatites and feral rocks
An ash fall at Mount Ontake
Birds. Dinosaurs. One in the same.
This week was the annual week of the Mount Hope Cemetery field trip for my Introduction to the Geological Sciences course. It’s a short walk from the classroom, so it’s ever a great opportunity to see “rocks in the wild.” In this case, I consider them ‘feral’ rocks, because they’ve escaped containment and have been living in the elements for many, many years.
One favorite stop is “Bubblegum Rock,” a large chunk of pink quartz.
Students are challenged to figure out the origin of the rock. Some do. Some don’t. But all are fascinated by it.
This piece of quartz is an example of a pegmatite. Pegmatites are huge minerals that grow under very specific circumstances. In the case of these giant quartz grains, they were the result of extremely slow cooling of magma well below the Earth’s surface.
Last Saturday, eruptions began on Mount Ontake, a volcano and popular hiking spot in Japan. At least 47 people are known to have been killed, overwhelmed by gas and ash spewing from the volcano.
Like many volcanoes, those of Japan are also part of the “Ring of Fire,” where the crust under the Pacific Ocean is being subducted or pulled beneath – in this case – the islands of Japan. In fact, Japan would not exist were it not for the subduction occurring there. The islands are purely volcanic.
This same subduction zone is also what was responsible for the massive 2011 earthquake that devastated parts of Japan and affected the entire margin of the Pacific Ocean.
There is forever discussion about the origins of birds within the science of paleontology. The general consensus has been, gee, for as long as I’ve called myself a paleontologist, that birds are dinosaurs. It’s just that modern dinosaurs happen to be able to fly (for the most part).
People have wanted to know how that happened. How do you go from a ground-walking animal to a flying one?
It turns out that it’s really not all that hard. The earliest ‘birds’ and their closest ‘dinosaur’ ancestors aren’t all that different. In fact, if you saw the early birds and their ancestors in the same forest, you might not even make a distinction between the two.
A new statistical analysis by Stephen Brusatte and others (sorry, paywalled) looked at the physical characteristics that distinguish ‘birds’ from ‘dinosaurs.’ Their study showed that these features accumulated over vast amounts of time, and once assembled, rapid evolution took place resulting in the origin of the creatures we now recognize as birds.