What are drumlins and eskers formed by?

Drumlins and Eskers: Nature’s Quirky Ice Age Leftovers

Ever stumble across a landscape that just feels… different? Maybe a little lumpy, a little winding, like Mother Nature had a playful moment after a really, really big freeze? Chances are, you might be looking at drumlins and eskers – two of the coolest (pun intended!) landforms left behind by the last ice age.

Drumlins: Those Funny, Streamlined Hills

Picture this: you’re walking across a field, and suddenly, you notice a bunch of smooth, rounded hills popping up. They look a bit like someone buried a bunch of eggs, pointy end down. Those, my friend, are likely drumlins. These little guys are basically hills made of glacial till – that’s just a fancy way of saying “a whole bunch of unsorted sediment” that the glaciers dumped as they moved. The name “drumlin” actually comes from the Gaelic word for “little ridge,” which is pretty spot-on.

What’s really neat is that drumlins usually hang out in groups, called drumlin fields. Sometimes they’re so packed together, they create this wild “basket of eggs” look to the landscape. And here’s the kicker: the long side of each drumlin points in the same direction that the ice was flowing way back when. So, they’re like little arrows pointing to the past! The front of the drumlin (the side that faced the glacier) is usually steeper, while the back gently slopes away, showing you which way the ice was headed.

How drumlins actually form was a head-scratcher for scientists for ages. But the current thinking is that they’re sculpted by the movement of sediment and water underneath the massive ice sheets. The sheer weight of the ice squishes the wet sediment, causing it to mold itself into these streamlined shapes. Some drumlins might have been built up layer by layer, while others are what’s left after the ice eroded everything else away. And some are probably a bit of both! You might even find some with gravel inside, or even solid rock hiding beneath the surface.

Drumlins come in all sizes, but they’re usually a few hundred meters long and wide, and maybe 15-30 meters high. But get this: the ratio of their length to width can actually tell you how fast the glacier was moving! Talk about a landform with secrets! If you want to see some seriously impressive drumlin fields, head to places like Wisconsin, New York, or even Ireland. You won’t be disappointed.

Eskers: Winding Roads from Meltwater Rivers

Now, let’s switch gears and talk about eskers. Imagine a long, snake-like ridge winding its way across the landscape. That’s an esker! Unlike the lumpy drumlins, eskers are made of layers of sand and gravel. Think of them as the fossilized remains of ancient meltwater rivers that used to flow inside, on top of, or underneath the glaciers. The word “esker” itself is Irish, meaning a ridge or elevation.

Most scientists believe that eskers formed inside tunnels carved by streams flowing beneath the ice. These tunnels acted like pipes, carrying sediment that the meltwater had eroded from the glacier bed. As the ice melted away, these sandy and gravelly riverbeds were left behind as winding ridges. Eskers can also form on top of glaciers, when sediment builds up in channels or cracks in the ice, or even in little bays along the glacier’s edge.

The path an esker takes is often dictated by the water pressure inside those subglacial tunnels. Sometimes, the pressure would force the esker to follow the direction of the glacier. Other times, it would push the water towards the lowest points, like valleys or riverbeds, even if that meant veering away from the glacier’s direct path.

Eskers can be short and sweet, or stretch for hundreds of kilometers! They’re usually between 5 and 50 meters high, and up to 500 meters wide. The sediment inside is typically pretty well-sorted, with different sizes of grains settling out in different layers. And if you look closely, you might even see patterns in the layers that show you which way the water was flowing.

You can find amazing eskers in places like Maine, Canada, Ireland, and Sweden. The Thelon Esker in Canada is a monster, stretching for almost 800 kilometers! Because they’re full of sand and gravel, eskers are often used as quarries for construction. In fact, some roads, like the Denali Highway in Alaska, are even built along eskers to save money. Pretty cool, huh?

A Glacial Legacy

So, there you have it: drumlins and eskers, two quirky and fascinating landforms that tell the story of the last ice age. Drumlins give us clues about how glaciers moved, while eskers reveal the hidden rivers that flowed within them. Next time you’re out exploring, keep an eye out for these icy leftovers. You never know what secrets they might reveal!