Shaping of the Earth's Surface Class 9: Notes and Questions

What Shaping of the Earth's Surface is about

Weightage: CBSE has not yet published marks for Class 9 Social Science 2026-27: its syllabus says the course structure "will be provided shortly". Class 9 is a school examination (80 marks annual paper + 20 internal assessment), so your school sets the paper.Source: CBSE Social Science syllabus, Class IX 2026-27

Key concepts

Interior of the Earth

NCERT section Plate Tectonics

The Earth has three main layers:

• Crust: the thin outer layer we live on; about 30-40 km thick under continents but only 5-7 km under oceans.
• Mantle: very thick and hot, mostly solid; the layer between the crust and the outer core.
• Core: extremely hot and heavy. The outer core is fluid, mainly iron and nickel; the inner core is a solid, spinning metal ball and the densest part of the Earth.

Two more terms matter for plate movement:

• Lithosphere = crust + upper mantle; a rigid outer shell broken into tectonic plates (about 100 km thick in the book's figure).
• Asthenosphere = the hot, partly molten, mobile layer just below the lithosphere; because it is semi-molten, the plates above it can move.

Worked example

Distinguish between the lithosphere and the asthenosphere. (2 marks)

Try it first, then show the solutionSolution

1. Lithosphere: rigid; crust plus upper mantle; broken into plates.
2. Asthenosphere: below it; hot, partly molten and mobile; lets plates move.

Answer: The lithosphere is the rigid outer layer made of the crust and the upper mantle; it is broken into tectonic plates. The asthenosphere lies beneath it; it is hot, partly molten and mobile, which allows the plates above to move slowly.

Theory of plate tectonics

NCERT section Plate Tectonics

The book credits the theory to W.J. Morgan. Its main idea: the Earth's outer layer is not one piece but is broken into large and small slabs of solid rock called tectonic plates. They float over the semi-molten layer beneath and move very slowly, usually a few centimetres a year.

Types of plates: continental (carry continents), oceanic (carry ocean floors) and mixed (carry both).

Major plates named in the book: Pacific, Eurasian, African, North American, South American, Indo-Australian and Antarctic.

Why they move: heat from the core makes molten mantle material rise while cooler material sinks. This circular flow is a convection current, and it pushes and pulls the plates in different directions.

Plate movement explains mountains, valleys, ocean basins, volcanoes, earthquakes and even where the continents and oceans lie today.

Worked example

What causes tectonic plates to move? Explain in about 50 words. (3 marks)

Try it first, then show the solutionSolution

1. Heat source: the Earth's core heats the mantle.
2. Hot molten material rises; cooler material sinks: convection currents.
3. These currents push and pull the plates over the semi-molten asthenosphere.

Answer: Heat from the Earth's core warms molten material in the mantle, which rises, while cooler material sinks. This continuous circulation forms convection currents. The currents push and pull the rigid plates of the lithosphere, which can move because the asthenosphere below them is semi-molten. The plates move only a few centimetres a year.

Plate boundaries and their effects

NCERT section Plate Tectonics

Where plates meet is a plate boundary. There are three kinds:

Boundary	Movement	What happens	Example
Convergent	plates move towards each other	two continental plates collide: fold mountains; oceanic meets continental: oceanic plate sinks below, causing volcanoes and earthquakes	Himalaya
Divergent	plates move apart	magma rises and forms new crust: mid-ocean ridges	Mid-Atlantic Ridge
Transform	plates slide past each other	crust neither made nor destroyed; mainly earthquakes	San Andreas Fault (USA)

Most earthquakes and volcanoes occur along plate boundaries, especially around the Pacific Ocean, the Ring of Fire. That is why the theory helps identify earthquake- and volcano-prone regions and plan for disasters.

Worked example

The Himalaya and the Mid-Atlantic Ridge were both formed by plate movement, yet they are very different. Explain why. (3 marks)

Try it first, then show the solutionSolution

1. Himalaya: convergent boundary; continental plates collide; crust folds upward.
2. Mid-Atlantic Ridge: divergent boundary; plates move apart; magma rises to make new crust.
3. So the direction of movement decides the landform.

Answer: The Himalaya formed at a convergent boundary, where two continental plates pushed into each other and the crust folded into high mountains. The Mid-Atlantic Ridge formed at a divergent boundary, where plates move apart and rising magma creates new crust on the ocean floor. The opposite directions of movement produce opposite results.

Weathering

NCERT section Process of Weathering and Erosion

Weathering is the breaking down of rocks on the Earth's surface into smaller pieces. The key point: it involves no movement of the broken material, only breaking.

Three types:

• Physical: rocks break because of temperature changes (heating and cooling), frost or wind.
• Chemical: minerals in rocks change through reactions with water, air or acids, forming new substances.
• Biological: caused by plants, animals or micro-organisms; for example, roots growing into cracks split the rock.

Weathering shapes the surface and is the starting point of soil formation.

Worked example

A peepal tree grows out of a crack in an old fort wall and the crack widens over the years. Which type of weathering is this? Give a reason. (2 marks)

Try it first, then show the solutionSolution

1. The agent is a living thing (plant roots).
2. So it is biological weathering.

Answer: Biological weathering. The growing roots of a living plant push into the crack and split the rock apart.

Erosion and its effect on livelihoods

NCERT section Process of Weathering and Erosion

Erosion is the wearing away of soil, rock and other material and its carrying from one place to another by natural agents: water, wind, ice or waves. Unlike weathering, erosion moves the material.

Types: water erosion (rivers, rain, waves), wind erosion (dry, sandy areas), glacial erosion (moving ice scrapes and carries rock) and coastal erosion (waves wear away the shore).

Erosion affects people's work directly:

• Farmers lose fertile topsoil, so yields fall.
• People near rivers and coasts lose land, houses and roads.
• Construction and mining face unstable land and safety risks.
• Tourism and fishing suffer when beaches, rivers and fertile lands are destroyed.

Traditional conservation in India (book's box): the Sindhu-Sarasvatī civilisation used contouring, bunding, terracing, dams and canals; the Zabo system of Nagaland uses earthen bunds on hill slopes; check dams slow streams so soil settles and groundwater recharges.

Worked example

Differentiate between weathering and erosion. (3 marks)

Try it first, then show the solutionSolution

1. Weathering: breaking of rocks in place; no movement.
2. Erosion: wearing away and transport of material by agents.
3. Agents of erosion: water, wind, ice, waves; weathering can be physical, chemical or biological.

Answer: Weathering is the breaking down of rocks into smaller pieces where they lie; the material is not moved. It may be physical, chemical or biological. Erosion is the wearing away of soil and rock and their transport to another place by agents such as running water, wind, ice or waves. In short, weathering breaks; erosion breaks and carries.

Agents of gradation and river landforms

NCERT section Agents of Gradation

Agents of gradation are natural forces that wear down, transport and deposit material, slowly levelling the surface: they lower high areas and fill up low ones. The five agents: running water, glaciers, wind, waves and groundwater.

Rivers work in three courses:

• Upper course (steep, fast): V-shaped valleys, waterfalls, rapids. A waterfall forms where hard rock resists erosion and softer rock below is worn away, creating a sudden drop. Uses: tourism, hydroelectric power, recreation, cultural value.
• Middle course: the river bends into meanders: it erodes the outer bank and deposits on the inner bank. A loop cut off becomes an oxbow lake; floodplains form. Meanders give fertile soil, attract villages, and help navigation and irrigation (e.g. the Grand Anicut or Kallanai in Tamil Nadu).
• Lower course (slow): heavy deposition forms deltas, levees and alluvial fans. A delta is a fan-shaped or triangular deposit at a river's mouth; very fertile (rice, jute), rich in fish, densely settled, but flood-prone. Example: the Sundarbans delta.

Worked example

Why are waterfalls found in the upper course and deltas in the lower course of a river? (3 marks)

Try it first, then show the solutionSolution

1. Upper course: steep slope, strong erosion; hard rock over soft rock gives a sudden drop.
2. Lower course: river slows, loses energy, deposits sediment at its mouth.
3. So erosion features upstream, deposition features downstream.

Answer: In the upper course the slope is steep and the river erodes strongly; where hard rock sits above softer rock, the soft rock is cut away and a sudden drop, a waterfall, forms. Near the mouth the river slows down, loses energy and drops the sediment it carries, building a fan-shaped delta. Erosion dominates upstream, deposition downstream.

Coastal, glacial, wind and underground-water landforms

NCERT section Agents of Gradation

Waves and currents (coast):

• Deposition: beaches (sand, pebbles; tourism, fishing, a natural barrier against waves) and sand bars.
• Erosion: cliffs (waves undercut the base), wave-cut platforms (flat area left as cliffs retreat), caves, arches (caves on two sides of a headland meet) and stacks (pillars left when an arch collapses).

Glaciers:

• Erosion: U-shaped valleys, cirques (bowl-shaped hollows at the head of a glacier), aretes (sharp ridges), hanging valleys, fjords (sea floods a glacial valley).
• Deposition: moraines, made of till: lateral (sides), terminal (end, furthest advance), medial (two glaciers meet). Moraines give fertile soil and can dam lakes. Glaciers also feed rivers with fresh water.

Wind (deserts):

• Erosion: yardangs (streamlined rock ridges), ventifacts (rocks polished by sandblasting), deflation hollows (blowouts), desert pavements.
• Deposition: dunes: barchan (crescent, one wind direction), longitudinal (parallel to wind), star (winds from many directions), parabolic (U-shaped, held by vegetation). Dunes check desertification and protect coasts.

Underground water (limestone areas, karst topography): caves, stalactites (hang from the ceiling), stalagmites (rise from the floor), sinkholes or dolines, underground rivers.

Worked example

Arrange in the order in which they form along a headland: stack, cave, arch. Explain the sequence. (3 marks)

Try it first, then show the solutionSolution

1. Waves first erode weak rock: cave.
2. Caves on both sides meet: arch.
3. Arch roof collapses: stack (an isolated pillar).

Answer: Cave → arch → stack. Waves attack weak parts of the rock to make caves; when caves on opposite sides of a headland meet, an arch forms; when the arch collapses, an isolated pillar of rock, the stack, is left standing.

Landform disasters: landslides, avalanches, GLOFs, dust storms

NCERT section Landforms and Disasters

Some disasters belong to particular landforms.

• Landslides (hill slopes): natural causes are heavy continuous rain (water adds weight and reduces friction), earthquakes and eruptions, steep slopes and loose weathered rock. Human causes: deforestation, mining, road building, unplanned hillside construction, poor drainage.
• Avalanches (snowy steep slopes): heavy snowfall in a short time, weak snow layers, a sudden rise in temperature, strong winds piling snow unevenly; triggers include earthquakes, vibrations, skiing, trekking and construction.
• GLOFs (Glacial Lake Outburst Floods): rapid melting of glaciers swells glacial lakes held back by weak dams of ice or loose moraine; heavy rain or snow, or an earthquake, avalanche or landslide, can break the dam and release a sudden flood downstream. The book asks you to find out what caused the flood in Chamoli, Uttarakhand, in February 2021.
• Dust storms (deserts, semi-arid areas): strong winds lift loose dry soil; drought, low rainfall, sparse vegetation (deforestation, overgrazing, poor farming) and climate change make them more frequent.

The chapter also notes that India has had major earthquakes (e.g. Gujarat, 2001) and that Varāhamihira's Bṛihatsaṁhitā discussed earthquakes ('bhūkampa') long ago.

Worked example

How do human activities increase the risk of landslides? Give three ways. (3 marks)

Try it first, then show the solutionSolution

1. Deforestation removes roots that hold soil.
2. Mining and road cutting disturb the slope.
3. Unplanned buildings and poor drainage add weight and let water collect.

Answer: 1. Cutting forests removes the roots that bind soil on slopes. 2. Mining and road construction cut into hillsides and disturb the natural balance of slopes. 3. Unplanned building on hillsides and poor drainage add weight and let excess water collect, so the slope suddenly fails.

Landforms and human history

NCERT section Agents of Gradation

The chapter shows landforms shaping human life:

• River plains (Ganga, Nile, Brahmaputra, Indus) gave rise to farming societies and early cities.
• Mountains were barriers and protectors: the Himalayas shielded India yet passes such as the Khyber Pass allowed cultural exchange.
• Deserts like the Thar held back large settlements, yet trade routes such as the Silk Route crossed dry lands.
• Coasts and harbours opened sea trade and contact with faraway lands, which helped kingdoms in south India grow rich.

The closing idea: internal forces build, external forces wear down, and human life (climate, resources, settlement, culture) depends on the result. Understanding this helps us prepare for disasters and live sustainably.

Worked example

'Mountains acted both as barriers and protectors.' Explain with reference to India. (2 marks)

Try it first, then show the solutionSolution

1. Protector: the Himalayas shielded India from invasions.
2. Not a total barrier: passes like the Khyber allowed cultural exchange.

Answer: The Himalayas protected India by making invasions difficult, but passes such as the Khyber Pass still allowed people, goods and ideas to move, so cultural exchange continued.

Shaping of the Earth's Surface in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Interior of the Earth and Plate Tectonics
• Weathering, Erosion, Agents of Gradation and Landform Disasters

Shaping of the Earth's Surface: key facts

Layers of the Earth

1. 1.Crust (5-7 km oceanic; 30-40 km continental)
2. 2.Mantle
3. 3.Outer core (fluid, iron and nickel)
4. 4.Inner core (solid, densest)

Lithosphere = crust + upper mantle; asthenosphere = semi-molten layer below it.

Why plates move

1. 1.Core heat
2. 2.mantle material rises, cool material sinks
3. 3.convection currents
4. 4.push and pull on plates

Speed: a few centimetres per year.

Plate boundaries

• •Convergent (towards) = fold mountains, volcanoes
• •Divergent (apart) = new crust, mid-ocean ridges
• •Transform (slide past) = earthquakes

Himalaya | Mid-Atlantic Ridge | San Andreas Fault.

Weathering vs erosion

Weathering = break in place (physical, chemical, biological) | Erosion = wear away + carry (water, wind, ice, waves)

Movement is the difference.

River courses

Upper	V-valley, waterfall, rapids
Middle	meander, oxbow lake, floodplain
Lower	delta, levee, alluvial fan

Erosion upstream, deposition downstream.

Agent → landform

Glacier	U-valley, cirque, arete, fjord, moraine
Wind	yardang, ventifact, deflation hollow, dunes
Waves	cliff, cave, arch, stack, beach
Groundwater	cave, stalactite, stalagmite, sinkhole

Karst topography = groundwater landforms in limestone.

Four landform disasters

Landslide	slopes
Avalanche	snow slopes
GLOF	glacial lakes
Dust storm	dry lands

Each has natural and human causes.

How the school exam asks Shaping of the Earth's Surface

The question patterns to expect, and the method that works for each.

Tricks to remember Shaping of the Earth's Surface

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Plate boundaries: CDT

  Converge = Crash (mountains), Diverge = Divide (ridges), Transform = Tremble (earthquakes).

  Use it when: Matching boundaries with effects.

• Stalactite vs stalagmite

  Stalac-T-ite holds on Tight to the ceiling; stalaG-mite rises from the Ground.

  Use it when: Groundwater landforms.

• Weathering vs erosion

  Weathering = Wreck in place; Erosion = Exit (it moves away).

  Use it when: Distinguish questions.

• River courses

  Up: V and Waterfall; Middle: Meander and Oxbow; Low: Delta and Levee: 'Very Wet Mangoes Obviously Drip Lightly'.

  Use it when: River landforms in order.

• Five agents of gradation

  'Rivers Glide While Waves Gurgle': Running water, Glaciers, Wind, Waves, Groundwater.

  Use it when: Naming the agents.

• Coastal sequence

  Cave → Arch → Stack: 'CAS' (like cash: the sea spends the rock away).

  Use it when: Formation order on a headland.

Shaping of the Earth's Surface: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Shaping of the Earth's Surface

The slips examiners see most often, and what to write instead.

• ✗Mistake: Saying weathering moves rock

  Weathering and erosion are taught together.

  Wrong working

  Weathering breaks rocks and carries them to rivers.

  Right working

  Weathering only breaks rocks in place; erosion wears away and carries the material.

  ✓Do this: Always mention 'no movement' for weathering.

  Usually costs: 1 mark in a 3-mark distinguish answer.

• ✗Mistake: Linking the Himalaya to a divergent boundary

  Students remember 'mountains form at boundaries' without the direction.

  Wrong working

  The Himalaya formed where plates moved apart.

  Right working

  The Himalaya formed at a convergent boundary where continental plates collided.

  ✓Do this: Fold mountains = convergent; ridges = divergent.

  Usually costs: The full mark in an MCQ.

• ✗Mistake: Mixing up U-shaped and V-shaped valleys

  Both are valleys.

  Wrong working

  Rivers make U-shaped valleys in the upper course.

  Right working

  Rivers cut V-shaped valleys; glaciers carve U-shaped valleys.

  ✓Do this: V for riVer, U for the broad tongue of ice.

  Usually costs: 1 mark.

• ✗Mistake: Giving only natural causes of landslides

  The human side is skipped.

  Wrong working

  Landslides are caused by rain and earthquakes.

  Right working

  Heavy rain, earthquakes and steep loose slopes, plus human causes: deforestation, mining, road building, unplanned construction, poor drainage.

  ✓Do this: Split every disaster's causes into natural and human.

  Usually costs: 1-2 marks of a 3-mark answer.

• ✗Mistake: Unlabelled or wrongly labelled meander diagram

  Students draw a curve but do not show where erosion and deposition happen.

  Wrong working

  A wavy line labelled 'river'.

  Right working

  Arrow for flow; outer bank labelled erosion (steep bank); inner bank labelled deposition (bar); oxbow lake where a loop is cut off.

  ✓Do this: Label at least four parts and show flow direction.

  Usually costs: 1-2 marks in a diagram question.

NCERT exercise guide: Shaping of the Earth's Surface

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Shaping of the Earth's Surface

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which layer of the Earth is fluid and made mainly of iron and nickel?
   (a) Crust (b) Mantle (c) Outer core (d) Inner core

   Hint

   One core layer is solid, the other is not.

   Answer

   (c) Outer core

2. Q2 · 1 mark · Very short answerExam level

   Name the landform formed when a cave breaks through both sides of a headland.

   Hint

   It comes before a stack.

   Answer

   A sea arch.

3. Q3 · 1 mark · Very short answerExam level

   Which agent of gradation forms cirques and aretes?

   Hint

   Moving ice.

   Answer

   Glaciers.

4. Q4 · 1 mark · Assertion-reasonHarder exam level

   Assertion (A): Weathering helps form soil.
   Reason (R): Weathering carries rock material long distances.
   Choose (a)-(d) as usual.

   Hint

   Does weathering move material?

   Answer

   (c) A is true but R is false: weathering breaks rock in place; erosion carries it.

5. Q5 · 2 marks · Short answerHarder exam level

   Why are most earthquakes and volcanoes found around the Pacific Ocean? (2 marks)

   Hint

   Plate boundaries.

   Answer

   The Pacific is ringed by plate boundaries where plates collide, separate or slide past each other. Movement at these boundaries causes earthquakes and volcanic activity, so they cluster in the Ring of Fire around the Pacific.

6. Q6 · 3 marks · Short answerHarder exam level

   How does erosion affect people in construction, tourism and fishing? (3 marks)

   Hint

   One effect each.

   Answer

   Construction and mining: erosion destabilises land, making sites unsafe. Tourism: beaches and scenic river banks can be destroyed. Fishing: damaged rivers, coasts and beaches reduce fishing grounds. Erosion thus directly affects people's work and incomes.

7. Q7 · 5 marks · Long answerHOTS / competency

   Suppose a district in Rajasthan faces frequent dust storms. Give three causes from the chapter and two mitigation steps. (5 marks)

   Hint

   Dry soil, wind, vegetation.

   Answer

   Causes: strong winds lift loose, dry soil; prolonged drought and low rainfall dry out the soil; sparse vegetation due to deforestation, overgrazing or poor farming leaves land exposed; climate change can make storms more frequent. Mitigation: plant trees and shelter belts and protect grasslands from overgrazing to hold the soil; use farming methods that keep the ground covered.

8. Q8 · 3 marks · Short answerHarder exam level

   How have landforms influenced trade in Indian history? Use two examples from the chapter. (3 marks)

   Hint

   Desert routes and coasts.

   Answer

   Deserts such as the Thar limited large settlements but encouraged trade routes like the Silk Route. Coasts and harbours supported trade and contact with distant lands, helping south Indian kingdoms flourish. Mountain passes like the Khyber also allowed exchange.

9. Q9 · 2 marks · Source-basedHOTS / competency

   A photograph shows grey powder covering cars and roofs near a mountain. What could have caused this and what does it show about the Earth? (2 marks)

   Hint

   The book's Let's Explore photo on deposition.

   Answer

   A volcanic eruption that threw out ash, which settled on everything nearby. It shows that powerful internal forces of the Earth can push molten material and ash to the surface.

10. Q10 · 3 marks · Short answerHarder exam level

    Compare the uses of waterfalls and beaches to people. (3 marks)

    Hint

    Tourism is common to both; look for the differences.

    Answer

    Both attract tourists and boost the local economy. Waterfalls can be used for hydroelectric power and may have cultural or religious importance. Beaches support fishing, shell and sand collection, and act as natural barriers that protect coastal settlements from strong waves.

11. Q11 · 5 marks · Long answerHOTS / competency

    Your village is on a steep hill with new roads being cut. Prepare a four-point plan to reduce landslide risk. (5 marks)

    Hint

    Address each cause: trees, construction, drainage, slope.

    Answer

    1. Stop cutting trees and plant deep-rooted species on slopes to bind soil. 2. Build roads and houses only after checking slope stability; avoid unplanned construction on steep, loose slopes. 3. Provide proper drainage so rainwater does not soak and load the slope. 4. Use retaining walls and terraces on vulnerable stretches, and set up warnings during heavy rain. Each step answers a cause named in the chapter.

12. Q12 · 1 mark · Very short answerExam level

    Arrange the river landforms from source to mouth: delta, meander, V-shaped valley, oxbow lake.

    Hint

    Upper, middle, lower.

    Answer

    V-shaped valley, meander, oxbow lake, delta.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Who gave the theory of plate tectonics, according to the NCERT book?Show answer

   W.J. Morgan.

2. 2.What is the lithosphere made of?Show answer

   The crust and the upper part of the mantle.

3. 3.Name the three types of tectonic plates.Show answer

   Continental, oceanic and mixed plates.

4. 4.What is the Ring of Fire?Show answer

   The area around the Pacific Ocean where most earthquakes and volcanoes occur along plate boundaries.

5. 5.Give an example of a transform boundary.Show answer

   The San Andreas Fault in the United States.

6. 6.What is an oxbow lake?Show answer

   A lake formed when a meander loop of a river is cut off.

7. 7.What is till?Show answer

   Rocks, soil and debris carried and deposited by a glacier, forming moraines.

8. 8.Which dune is crescent-shaped?Show answer

   The barchan dune.

9. 9.What does GLOF stand for?Show answer

   Glacial Lake Outburst Flood.

10. 10.Name India's only mud volcano mentioned in the book.Show answer

    Baratang, in the Andaman and Nicobar Islands.

11. 11.What is the Zabo system?Show answer

    An integrated farming system of Nagaland that uses earthen bunds on hill slopes to conserve soil and water.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Internal forces (earthquakes, volcanoes, folding, faulting) build; external forces (weathering, erosion, deposition) wear down.
• ☐Layers: crust, mantle, core; outer core fluid (iron, nickel), inner core solid and densest.
• ☐Lithosphere (crust + upper mantle) is broken into plates; asthenosphere below is semi-molten.
• ☐Plates move a few cm per year, driven by convection currents from core heat.
• ☐Major plates: Pacific, Eurasian, African, North American, South American, Indo-Australian, Antarctic.
• ☐Convergent: Himalaya; divergent: Mid-Atlantic Ridge; transform: San Andreas Fault.
• ☐Ring of Fire: around the Pacific; most earthquakes and volcanoes.
• ☐Weathering: physical, chemical, biological; no movement.
• ☐Erosion: water, wind, glacial, coastal; harms farming, homes, mining safety, tourism, fishing.
• ☐Agents of gradation: running water, glaciers, wind, waves, groundwater.
• ☐River: V-valley, waterfall (upper); meander, oxbow lake (middle); delta, levee (lower).
• ☐Glacier: U-valley, cirque, arete, hanging valley, fjord; moraines: lateral, terminal, medial.
• ☐Wind: yardang, ventifact, deflation hollow, desert pavement; dunes: barchan, longitudinal, star, parabolic.
• ☐Groundwater (karst): caves, stalactites, stalagmites, sinkholes, underground rivers.
• ☐Disasters: landslides, avalanches, GLOFs, dust storms; natural plus human causes.

Shaping of the Earth's Surface: frequently asked questions