- Eskers are long, winding ridges made by melting glaciers.
- Eskers are made of sand, gravel, and rocks of different sizes.
- Eskers stick up higher than the land around them.
- Eskers show how glaciers moved and melted long ago.
- Eskers give us sand and gravel for building things.
- Roads and railroads are built on eskers because they are firm.
What is an esker and how is it formed?
An esker is a long, winding ridge of sand, gravel, and rocks that was made by melting glaciers. Glaciers are huge sheets of ice that move very slowly over land. As glaciers melt, water runs through tunnels under the ice or flows in channels on top of the ice. This melting water carries sand, pebbles, and rocks as it flows. When the glacier finally melts away, the sand and rocks are left behind in a winding ridge called an esker.
Eskers can range from 100 meters to 100 kilometers long! They are made up of all sizes of materials from fine sand grains to big boulders. The finer sandy stuff is usually found near the top of the esker. The bigger rocks and boulders are deeper down. Eskers have steep sloped sides of 25-30 degrees.
Scientists think eskers are channel deposits. This means they were left on the ground when the melting glacier water flowed away in streams under or on top of the ice. As the glacier retreated or shrank back, it left the esker ridges behind.
How do eskers form and what are they made of?
Eskers form when glaciers melt. The melting water runs through tunnels under the ice or flows in channels on top of the ice. This water carries sand, pebbles, gravel and rocks along with it. When the glacier finally disappears, all this material is left behind in a long winding ridge called an esker.
Eskers are made up of all sizes of materials that were carried by the flowing meltwater. There can be fine grains of sand, small pebbles, gravel, rocks and even some big boulders! The finer sandy bits are usually found closer to the top of the esker. The bigger rocks and boulders get left deeper down inside the esker ridge.
Eskers have steep angled sides, about 25-30 degrees. The sides were formed by the melting streams eroding away at the ice tunnels. When the ice melted, it left behind the steep esker ridges made of sand, gravel and rocks.
How do eskers show the past movement of glaciers?
Eskers give scientists clues about how ice sheets and glaciers behaved in the past. By studying eskers, scientists can reconstruct what the surface of ancient glaciers looked like. They can also figure out which way the end of the glacier was pointing.
The long winding shape of eskers shows the path the melting water took under the glacier. So eskers trace out how the glacier moved and melted long ago in that spot. The length of the esker shows how far the ancient glacier extended. And the materials in the esker reveal details about how fast the melting water flowed.
So eskers act like geological history books! They record useful information about what glaciers were doing thousands or millions of years ago. Without eskers, we would know much less about Earth’s past glacial periods.
How high are eskers compared to the land around them?
One key fact about eskers is that they stick up higher than the land around them. Eskers form long, winding ridges that rise up above the flat ground around them. An esker ridge can rise up 5-50 meters above the surrounding terrain.
This happens because eskers are leftovers from what were once ice tunnels or meltwater channels inside a glacier. This left a winding “gap” space where the ice used to be. Later when everything melted, the esker material filled in the gap, but it rose up higher than the regular flat land.
Also, materials in eskers like sand, gravel and rocks are more resistant to erosion than the soils around them. So even after thousands of years, eskers still stand out as elevated ridges winding across the landscape.
How are eskers used for getting sand and gravel?
An important use of eskers is that they provide us with sand and gravel for building things. Sand and gravel are mixed with cement to make concrete. They are also used to make asphalt for paving roads. We need huge amounts of sand and gravel for construction projects.
Eskers are ideal sources because they are made up of different sizes of loose sediments like sand and gravel. Also, eskers are raised up above the ground, so the materials are easy to access. Digging into eskers is much easier than removing rocks and dirt from the earth.
Many eskers are hundreds of kilometers long. So they contain incredibly massive amounts of sand and gravel for mining and extracting. Eskers are mined using excavators and bulldozers that dig into the ridges to collect the sandy sediments. This material is processed and then transported for construction uses.
Why are roads and railroads built on eskers?
Because eskers form raised ridges that are dry and firm, they make excellent foundations to build roads and railroads. The loose rocks and gravel in eskers provide better drainage than wet muddy soil. This means the esker surface is drier and more stable.
Also, building roads on the higher esker ridges means less earthwork is needed. There is no need to flatten hills or fill in low areas to make an even roadbed. The winding esker ridge already provides a ready-made raised foundation.
Railroad companies also prefer to lay down tracks on eskers because the coarse gravel provides excellent drainage for the wooden railroad ties or concrete foundations. This prevents water from pooling under the tracks and shifting the ground. It helps keep the rails firmly fixed in place.
So next time you are driving or riding on a road or railroad that makes some winding curves, there may be an ancient esker ridge underneath!
What are some facts about eskers?
Here are some interesting facts about eskers:
- Eskers can range in length from 100 meters to over 100 kilometers – how long is that?!
- The steepest esker sides have angles of about 25-30 degrees. That’s pretty steep!
- Eskers usually wind across the landscape in sinuous S-shaped curves.
- Smaller sediments like sand and pebbles are found near the top of eskers.
- Bigger boulders can be found deeper down in eskers.
- Eskers stick up 5-50 meters higher than the surrounding land.
- Eskers provide sand, gravel and rocks for building materials.
- Roads and railroads are often built on eskers because they drain well.
How do geologists study and date eskers?
Geologists use eskers to learn about past glaciers. They study the length, shape, and material to understand how glaciers moved and melted. But how do they know how old eskers are?
Scientists use radiocarbon dating to estimate the age of organic material in eskers. This gives the minimum age for when the glacier melted there.
They can also look at layers above and below the esker to bracket the time range. For example, if there is lava underneath an esker dated to 10,000 years ago, the esker must be younger than that.
Geologists may also use optical stimulated luminescence dating on sand grains in an esker. This gives the last time the sand was exposed to light before burial.
Using these methods, geologists can determine if an esker formed 10,000 years ago or 100,000 years ago during different ice ages!
The age and features of eskers give us amazing clues about Earth’s glacial past periods. Eskers are like history books made of sand, gravel and stone!
How do I learn more about eskers?
Eskers are really interesting geologic formations with an important role in studying past glaciers! Here are some ways to find out more:
- Read books about glacial geology and look at diagrams of how eskers form.
- Watch online videos explaining the process of melting water carving out tunnels in ice sheets.
- Look at aerial photos or satellite images showing eskers winding across the landscape.
- Visit an esker in person and observe the materials and steep sides.
- Go to a museum and ask if they have a small scale model or cross-section of an esker that you can look at.
- Make a model esker using sand and gravel in a small stream table at home.
- Talk to a geologist who has studied eskers and glacial geology. Ask them questions!
The more you learn about eskers, the better you’ll understand Earth’s past glacier periods and icy landscapes. Figuring out our planet’s history is like solving an exciting mystery