December 15, 2010

Geology Word of the Week: G is for Gondwana

Posted by Evelyn Mervine

Gondwana reconstruction. Image from Wikipedia Commons.

This week we are at the letter G… I immediately thought of one of my favorite geology words: Gondwana!

def. Gondwana:
Gondwana is an ancient geological supercontinent that was comprised of modern-day Antarctica, South America, Africa, Australia, New Zealand, India, and Arabia. Gondwana first formed ~500 million years ago and later joined with the supercontinent Laurasia, that was comprised of modern-day North America, Europe, and Asia, to form a super-supercontinent named Pangea. Subsequently, Pangea began breaking up ~175 million years ago. The first stage of that separation was rifting of Laurasia from Gondwana. Eventually, all of the modern-day continents formed and gradually moved (over the past ~175 million years) into their present positions.

I love thinking about past supercontinents and super-supercontinents. Think about how different the planet must have looked: one massive continent and one massive ocean only. Imagine trekking across that massive continent or trying to sail across that massive ocean– which was called Panthalassia, by the way. What great names: Pangea and Panthalassia. Imagine how much easier geography class must have been back then (purely hypothetically, that is, since there were no humans). No memorizing the 7 continents and various oceans in primary school. Just one land and one ocean to remember.

Pangea is not the only supercontinent in Earth’s history, just the most recent one. Geologists believe that there have been several cycles of supercontinents forming and breaking up. Of course, the further back one goes in geologic time the sparser the evidence (much is destroyed in cycles of continents forming and breaking up), so much less is known about these earlier supercontinents. However, geologists have given them very cool-sounding names: Pannotia, Rodinia, Columbia, Kenorland, Ur, and Vaalbara.

There are many neat animations on the web showing the formation and break-up of Pangea and other past supercontinents. Here is one animation I like.