This video is important in understanding the effects of glaciers due to their large impact on landforms. Glaciers create large valleys, fjords, transport large rocks, and leave behind markers such as till, moraines, striations, and kettle lakes. These terms are discussed and explained throughout the video, leaving a greater knowledge on how our landscape was created.

Why Watch This Video?

  1. Have you ever wondered how large boulders end up in a bizarre location?
  2. Would you like to know how large valleys were created?
  3. Have you ever been confused by what defines a fjord?

Key Terms

Plucking: When water freezes into rocks and the force of the glacier breaks off a fragment of rock from its source and transports the fractured rock down the glacier. This is how large boulders can end up in far distances from their sources.

Abrasion: Abrasion is the scrape marks left behind from a moving glacier. It is a type of erosion. The cause of abrasion is from rocks that are frozen into the glacier that scrape along the bedrock.

Kettle Lakes: Kettle lakes are small lakes left behind from broken pieces of a glacier. These broken pieces of ice were buried from debris from the glacier. As the broken ice melted, it formed holes that later can become lakes, known as kettle lakes.

Loose Ends

Glacial Terminus

The video does a great job in explaining most terms mentioned in the video, although they seem to pass over this term that they mentioned. The glacial terminus is the end of the glacier. You may have heard it called the toe or snout of a glacier elsewhere.

Glacier Definition

At the beginning of the video, it defines a glacier as “a long-lasting mass of slow-moving ice and snow.” The text adds a key point that a glacier moves along the earth’s surface (559). Just a reminder that a glacier is a mass of ice and snow on land that is in motion.

Glacial Erratic

A rock transported and deposited by a glacier. A key point that may be missed in talking about erratics is that they are too large to be transported by a river or body of water.

5. Self-Test Questions

Scroll down to see the answers.

1. What is till?

  1. Unsorted debris left behind such as rocks and clay.
  2. Small shards of ice left behind a glacial route.
  3. Sorted rock debris left behind a glacier.
  4. Groves in the rock bed behind a glacial route.

2. How are U-shaped valleys made?

  1. Large rapid rivers cuting into the landscape.
  2. Created by plucking and abrasion from a glacier.
  3. The ocean flowing into land.
  4. Frozen pieces of ice that became buried, that later melted, creating long eroded land.

Question 3: What happens when water is freezes into rocks?

  1. The ice becomes tightly bonded to the rock.
  2. Trick question, ice cannot bond to rocks.
  3. Water rarely bonds to rocks because the ice freezes and splits from the rock.
  4. The ice causes the rock to break apart and quickly fall.

4. How did that large rock shown at the start of the video become jammed in between pine trees in Yellowstone National Park?

  1. The hippie rock climbers transported it to a place in the park they camp and boulder/ rock climb without getting in trouble.
  2. The area was once covered with large boulders like this, although till from a glacier covered the majority in the area, only leaving the tip of this boulder visible.
  3. The boulder is an erratic from the result of plucking.
  4. The parks police planted the trees around this fallen piece of rock from a nearby mountain to prevent the avid rock climbers from climbing the boulder.

5. What do we call large valleys that are flooded by risen sea levels?

  1. A river.
  2. A flood plain.
  3. A flooded valley.
  4. A fjord.


1. Answer A because till is the unsorted debris left behind a glacier made up of rocks, clay and sand.

2. Answer B is correct because valleys are created by erosion from a moving glacier.

3. Answer A. When water freezes into rocks, it creates tight bonds. This is explained in the video referring to plucking.

4.  Answer C. This large boulder is a result of plucking. It is not from the nearby mountains at the park but was carried by a glacier that began a far distance away.

5. Answer D. When a valley is filled by risen sea levels, it is called a fjord.

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