Glacier Lesson 7

Photographs by Thomas McGuire

Written by Martin Richard

We have been talking about glaciers. One way to think about glacier is, they are rivers of ice.

But sometimes glaciers can be much larger than rivers. They can be oceans of ice, like the glaciers that cover Antarctica and Greenland.

What would an ocean of ice do to the land beneath it? What would the land look like when the glaciers melt away?

Let’s start by thinking about rocks in fast-moving streams.

Stones in mountain streams are often round and smooth. How does that happen?

As the water moves them, they bump into other stones. Their corners and edges get knocked off, and they get round as they roll down the stream. As sand rubs against them –and they rub against sand– the smallest edges and corners get knocked off too, and they become polished and smooth. That takes a lot of rolling, so it takes a lot of time.

Now look at these pictures of mountains. The mountains on the bottom are all jagged and sharp. The mountains on the top are more round, more smooth.

So which of these mountains are older?

The ones that are round and smooth are older! Their edges have been worn off.

What could wear a mountain down? And how long does it take?

Water wears the mountain down. Water erodes it away. All those rocks moving down streams and rivers do not move back up the mountain.

Sometimes the water is ice! A glacier! Glaciers are like bulldozers –actually, several lines of very slow bulldozers– and push huge amounts of rock downhill.

Back to our first two questions: What would an ocean of ice do to the land beneath it? It would wear off the edges and corners of the land, making it rounder.

What would the land look like when the glaciers melt away? It would look like the mountains in the top picture!

Those worn-down mountains are in the Hudson Highlands in New York. There is good evidence that they were once covered completely by glaciers, sometimes a mile deep! These mountains were worn down by ice, lots and lots of ice, covering the whole landscape, pushing it down and wearing it away.

The mountains on the bottom are from the Rocky Mountains, in Colorado. They are still growing! They are very young compared to the old, rounded mountains in New York.

How long does it take to wear down a mountain?

Well, the evidence shows that the rounded mountains in New York stopped growing 250 million years ago. (That’s about 20 million years before the first dinosaurs.) So a good answer is, it takes a couple of hundred million years to wear a mountain down, to make a mountain smooth and round instead of jagged and sharp.

The original EPOD can be found here.

Comments

[Anna Elizabeth Wooten]

I wrote a story about a rock and its difficulties of being a rock from a different planet that arrived as a comet flew by our new forming earth.I was doing reasearch on the idea and I found out I could understand the research of rocks so much better. I enjoy learning. And what are the possiblity with quarks and matter, and how the earth works from inside. Pushing up rocks. They do not melt. So my story was really about rocks that do not melt, they get out and they just lay around. And if enough rocks with right elements can change the earth, and I think more students may want to find out about that like I did. Protons and atoms, there is so much more. It is amazing.

[Anna Elizabeth Wooten]

Please excuse my spelling. I found out a few years ago that I had a mind that is very smart, I did not know that before so I am making up for lost time. I am studing physics and using my creative ideas to ask the right question. To help students to think about they could change things if they wanted to, they could sit around and talk about the possibilities. Put it on paper. Students are the solutions working with their professors or teacher they see the next possibility.

[Anna Elizabeth Wooten]

I belive that climate is real, I also belive we have been this before, and our earth has shifted, when we had the earthquake in Japan. I have been reading about how the core of our eath works. And how we were in the ice a very long time before this ice age happened. Except it was near were our equator is now. We just rotated.

[Kebi]

Sure there's a lot of uncertainty with rgedras to actual attribution of disasters but if there's any admission of this you just know that the denialists will exploit it to convince the public climate change isn't real. The public is too stupid so we need to bend the rules and overstate the confidence, the stakes are too high; there's no time for accuracy! It's a little thing we call the "precautionary principle"./sarc