Welcome to Glaciated Landscapes!
Welcome! In this chapter, we are going to explore some of the most powerful "earth-sculptors" on our planet: glaciers. Imagine a massive, moving river of ice that is so heavy and strong it can grind down mountains and carve out entire valleys. By the end of these notes, you’ll understand how these ice systems work, the incredible shapes they leave behind, and how humans are changing these fragile environments. Don't worry if it seems like a lot of technical terms at first—we'll break them down using simple analogies you see every day!
1. Glaciated Landscapes as Systems
Geographers like to think of a glaciated landscape as a system. Think of it like a bank account: you have money coming in (deposits), money being used (spending), and a final balance at the end of the month.
A. Inputs, Processes, and Outputs
Inputs: These are things entering the system, like snow (precipitation) and solar energy.
Processes: This is the "action" happening, such as the ice moving or eroding the rock beneath it.
Outputs: These are things leaving the system, like meltwater, water vapor (evaporation), and moraine (rock debris).
B. Glacier Mass Balance
This is the "bank balance" of the glacier. We calculate it using this formula:
\( \text{Glacier Mass Balance} = \text{Accumulation (Inputs)} - \text{Ablation (Outputs)} \)
If accumulation is higher than ablation, the glacier grows (advances). If ablation is higher, the glacier shrinks (retreats).
C. Types of Glaciers and Movement
Not all ice is the same! The syllabus requires you to know two main types:
1. Valley Glaciers: Small "tongues" of ice that flow down mountain valleys.
2. Ice Sheets: Massive "pancakes" of ice that cover entire continents (like Antarctica).
How do they move?
Basal Sliding: Think of a bar of soap sliding across a wet floor. A thin layer of meltwater at the bottom of the glacier acts as a lubricant, letting the whole thing slide.
Internal Deformation: Imagine a deck of cards being pushed from the top. The cards at the top slide faster than the ones at the bottom. The ice crystals actually shift and slide over each other.
Quick Review: Warm-based vs. Cold-based Glaciers
Warm-based glaciers are in "warmer" areas (like the Alps). They have meltwater at the bottom, so they move fast via basal sliding.
Cold-based glaciers are in very cold areas (like the poles). They are frozen to the rock and move very slowly, mostly through internal deformation.
2. Sculpting the Land: Erosion and Deposition
Glaciers are like giant pieces of sandpaper. They don't just sit there; they actively change the shape of the Earth.
A. Geomorphic Processes (The Action)
Nivation: This is "snow-patch erosion." It’s a combination of freeze-thaw and meltwater weakening the rock under a patch of snow.
Plucking: The glacier freezes onto a rock and, as it moves, "yanks" the rock right out of the ground.
Abrasion: The rocks stuck in the bottom of the ice act like sandpaper, grinding and scratching the bedrock below.
B. Erosional Landforms (The Shapes Left Behind)
These landforms are created when a glacier takes away material:
Corrie (Cirque): An armchair-shaped hollow on a mountainside. Mnemonic: Corries are "Comfy" like armchairs.
Arête: A knife-edged ridge. This happens when two corries erode back-to-back.
Pyramidal Peak: A sharp, pointed mountain top (like the Matterhorn) formed when three or more corries meet.
Glacial Trough (U-shaped Valley): Unlike rivers that make "V" shapes, glaciers are wide and heavy, carving out deep "U" shapes.
Roche Moutonnée: A rock "bump" that is smooth on one side (abrasion) and jagged on the other (plucking).
Striations: Long scratches in the rock caused by stones trapped in the moving ice.
C. Depositional Landforms (The Dropped Debris)
When the ice melts, it drops everything it was carrying. This material is called Till (it's unsorted, meaning big rocks and tiny sand are all mixed together).
Moraines: Ridges of till. Terminal moraine is at the very front of the glacier; Lateral moraine is along the sides.
Erratics: Giant boulders that look "out of place" because the glacier carried them from a completely different area.
Drumlins: Egg-shaped hills. Imagine a spoon turned upside down in the mud. The "blunt" end faces the direction the ice came from.
Key Takeaway: Erosion happens when ice is moving and powerful. Deposition happens when the ice loses energy and melts.
3. Changing Climates and Post-Glacial Landscapes
Landscape systems change over time. When the climate warms up, the ice melts, and meltwater takes over the sculpting job.
A. Glacio-fluvial Landforms (Ice + River)
These are formed by running water inside or under a melting glacier. Unlike glacial till, these deposits are sorted (layers of similar-sized stones) because water is better at sorting than ice is.
Eskers: Long, wiggly ridges that look like "earth snakes." They are actually the remains of old riverbeds that ran in tunnels under the ice.
Kames: Mounds of sand and gravel.
Outwash Plains: Flat areas in front of a glacier where meltwater has spread out and dropped sediment.
B. Periglacial Landscapes (Near the Ice)
Periglacial means "around the edge" of glaciers. These areas are characterized by Permafrost (ground that is permanently frozen).
Patterned Ground: Frost heave pushes stones into geometric shapes like circles or polygons on the surface.
Pingos: Massive ice-cored mounds that look like "earth blisters."
4. Human Activity and Glaciated Systems
Humans often use these landscapes, but because they are so cold and fragile, our actions can cause big problems.
A. Human Activity in Periglacial Areas
In places like Alaska or Siberia, we extract oil and gas.
The Problem: Heat from buildings and pipes can melt the permafrost.
The Result: This creates Thermokarst—a landscape of hummocky ground and boggy hollows where the ground has collapsed because the ice holding it up has melted.
B. Human Activity in Glaciated Areas
We often build dams in glacial troughs for hydro-electric power (HEP).
The Impact: Dams trap sediment that should naturally flow downstream. This can lead to channel scour (the river downstream erodes its bed more deeply because it has no sediment to deposit) and changes the "energy balance" of the valley floor.
Did you know? Most of the gravel used in building roads in the UK comes from glacio-fluvial deposits (like old outwash plains and eskers) left behind thousands of years ago!
Quick Review Checklist
1. Can you explain the difference between accumulation and ablation? (Ice gained vs. ice lost).
2. Do you know the two main erosion processes? (Plucking and Abrasion).
3. Can you name one landform caused by ice sheets? (Till sheets or ellipsoidal basins).
4. What is a Pingo? (An ice-cored mound in a periglacial area).
5. How do humans cause Thermokarst? (By melting permafrost with heat from buildings/pipes).
Don't worry if these landforms are hard to visualize at first! Try to find a photo of a "U-shaped valley" or a "Corrie" online—once you see the "armchair" or the "U" shape, the names will stick much better!