Work of Moving Ice, Wind, and Sea Waves

Snowfields and the Snow-Line

In places where it’s always cold, snow doesn’t melt—it keeps building up. Over time, this snow becomes thick and turns into ice. These areas are called snowfields. They are always found above a certain height called the snow-line.

• A snowfield is a place always covered in snow and ice.
• The snow-line is the lowest level where snow stays all year.
• The height of the snow-line depends on temperature, snowfall, wind, and slope.

The snow-line is the lowest point where snow stays all year. But this height changes depending on a few things:

• Latitude: Near the equator (hotter areas), the snow-line is higher. Near the poles (colder areas), it’s lower—sometimes at sea level.
• Snowfall: If more snow falls than melts, the snow-line is lower.
• Wind: Hot, dry winds melt snow quickly, raising the snow-line. Cold, moist winds help snow stay, lowering it.
• Slope: On steep slopes, snow slides off easily, so the snow-line is higher. On gentle slopes, snow stays longer, so the snow-line is lower.

In super cold places, it snows all the time—and that snow doesn’t melt much. Instead, it builds up year after year and turns into thick ice. These permanently frozen areas are called snowfields. But snowfields only form above a certain height, called the snow-line. Think of it as the “magic line” on mountains above which snow stays all year.

What Is a Glacier?

In snowy regions, fresh snow keeps building up in layers year after year. The weight of these layers squashes the snow at the bottom, making it hard, grainy, and compact. This process even melts some snow, which refreezes and turns into granular ice.

Eventually, this huge, solid mass of ice becomes a glacier—a slow-moving river of ice! It flows downhill under its own weight, but at a very slow pace—just a few centimeters to a few meters per day.

Types of Glaciers

There are two main types of glaciers, depending on where they form:

Continental Glaciers

• Huge ice sheets that cover vast areas.
• They form in cold regions like Antarctica and Greenland.
• These glaciers build up in the center and spread outward in all directions.
• They can be thousands of meters thick!

Valley Glaciers

• These form in high mountains.
• Ice starts flowing down existing valleys—fitting their shape.
• In wide valleys, glaciers spread out.
• In narrow valleys, they squeeze and move like toothpaste from a tube!

Examples from India

• Siachen Glacier in the Karakoram range — about 72 km long.
• Gangotri Glacier in Uttarakhand — 25.5 km long.
• Rivers like the Ganga and Yamuna begin from glaciers: Gangotri and Yamunotri.

How Glaciers Shape the Land

Just like rivers, glaciers perform three major jobs: erosion, transportation, and deposition. Even though they move slowly and affect smaller areas, glaciers leave BIG marks on the land!

Erosion by Glaciers

As glaciers flow over land, they pick up rocks, gravel, and sand. These materials act like tools that scrape and scratch the surface beneath—almost like a giant icy bulldozer! Here are the main landforms created by this erosive action:

Cirque

• A bowl-shaped hollow found at the start of a glacier.
• It forms where ice collects and digs into the rock.
• Sometimes, water fills this hollow later—creating a small lake called a tarn.

U-Shaped Valley

• Unlike rivers that carve V-shaped valleys, glaciers reshape existing valleys.
• They make the valley deeper, wider, and smoother—resulting in a shape like the letter “U.”
• These valleys have flat bottoms and steep, straight sides.

Hanging Valley

• Small glaciers (called tributary glaciers) join the larger main glacier.
• But they don’t erode as deeply, so their valleys are higher up.
• After the ice melts, these high-up valleys look like they’re “hanging” above the main one.

How Glaciers Carry and Deposit Material

Glaciers may be slow movers, but they’re mighty transporters! As they slide downhill, they pick up everything from tiny grains to huge boulders. This load of rocks and soil is called the glacial load, and it comes from:

• Mountain slopes
• Valley sides
• Valley floor
• Even the air!

Transportation by Glaciers

Glaciers gather and drag this rocky material as they move. It’s like an icy conveyor belt, shifting chunks of the landscape from one place to another.

Deposition by Glaciers

When glaciers melt or pull back (called retreating), they drop their load in different spots. These leftovers form piles called moraines. Depending on where they’re placed, moraines are grouped into four types:

Terminal Moraine

• Found at the very end of the glacier.
• Looks like a ridge made of clay, gravel, and boulders.

Lateral Moraine

• Found along the sides of the glacier.
• Made from debris fallen from valley walls.

Medial Moraine

• Created when two glaciers meet and their side moraines merge.
• Forms a dark line running down the center of the combined glacier.

Ground Moraine

• Found underneath the glacier.
• A mix of fine and coarse material left behind after the glacier melts.

How Wind Shapes the Land

Wind is a powerful sculptor in dry regions like deserts. Since there’s little vegetation and lots of loose soil, the wind gets plenty of material to work with. It performs the classic trio of:

• Erosion: Breaking rocks into smaller pieces
• Transportation: Carrying those pieces away
• Deposition: Dropping them when the wind slows down

Erosion by Wind

Wind erosion happens mostly with the help of sand particles. These tiny grains act like sandpaper and wear down rocks. It works in three ways:

1. Abrasion – Sand grains hit and scratch surface rocks, slowly wearing them away.
2. Attrition – Sand particles crash into each other, getting rounder and smoother.
3. Deflation – Wind blows away loose particles from the ground, creating hollows.

Landforms from Wind Erosion

Let’s look at a few special shapes the wind creates:

Mushroom Rocks (Rock Pedestals)

• Rocks with layers—some hard, some soft.
• Wind erodes the softer lower part faster, leaving the top like a wide cap.
• Result: rocks shaped like mushrooms!
• Seen in Sahara Desert and near Jodhpur in India.

Wind-Eroded Basins

• Strong wind blows away small particles from dry ground.
• Over time, it creates bowl-shaped hollows or basins.
• Famous example: Quattara Depression in Egypt.

How Wind Moves and Drops Sand and Dust

We’ve already seen how wind breaks things down. Now let’s explore how it carries and drops materials to reshape the land.

Transportation by Wind

Wind can carry all kinds of tiny things:

• Dust, smoke, pollen, fine sand, even seeds.
• In dry areas with loose soil and no trees, wind lifts loads of particles.
• These can travel very far—even hundreds or thousands of kilometers!

Examples:

• Wind from the Gobi Desert carries dust all the way to northern China.
• In India, winds from the Thar Desert bring dust to Western Uttar Pradesh, Haryana, and Punjab, making soil fertile there.

Deposition by Wind

Eventually, the wind drops what it’s carrying. This happens when:

1. Wind is overloaded with dust.
2. Wind slows down and loses strength.
3. Wind hits an obstacle (like a bush or rock) and has to rise over it—slowing down and dropping particles.

Landforms Made by Wind Deposition

Let’s look at some cool shapes formed when wind drops sand:

Sand Dunes

• Hills made of sand—common in deserts.
• They can move or stay still, depending on wind and obstacles.
• If bushes or trees grow, the dunes become fixed and stop moving.

There are two main types:

Barkhans

• Crescent-shaped dunes.
• Form when sand piles up behind an obstacle.
• Found in places with strong one-direction winds, like the Sahara Desert.

Seif Dunes

• Long, narrow ridges running parallel to wind direction.
• Made when swirling winds deposit sand along the sides of open spaces.
• Seen in the Thar Desert.

Loess

• Fine dust deposited far from its source.
• Looks like yellow or brown soil—great for farming!
• Major deposits found in Northern China, Germany, and parts of India.
• The Yellow River in China gets its name from this yellow dust!

How Sea Waves Shape the Land

Sea waves are always in motion, especially near coastlines. Like rivers and glaciers, they perform the three familiar tasks:

• Erosion – Breaking down rocks
• Transportation – Carrying broken pieces
• Deposition – Dropping materials to form new landforms

Waves help reshape coastlines by wearing away rocky areas and building up new coastal features.