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Unit 5: Atoms, purity and climate

Climate and ice ages — HIA International - Grade 7 Revision Notes & Topical Questions

5 min read 9 parts Lesson 5 of 6 3 quizzes

📚 HIA International - Grade 7 Hub / Topical Revision
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Lesson summary

5.4 Climate and ice ages — HIA INTERNATIONAL notes: Describe past climate change, glacial and interglacial periods, ice ages and the evidence for them.Glacial period = a very cold period when much of the Earth was frozen.Interglacial period = a warmer period between glacial perio…

  • Last glacial
  • Earlier times
  • Earth's orbit and tilt
  • Sun's output
  • Moving continents
  • Without it

Part 1 of 7Glacial and interglacial periods

1Glacial period
Glacial period a very cold period when much of the Earth was frozen.
2Interglacial period
Interglacial period a warmer period between glacial periods, and the Earth is in one now.
3Last glacial
  • Last glacial lasted until about 10 000 years ago.
4Cycles
  • Cycles over the last 450 000 years the climate has swung between glacial and interglacial periods.

Part 2 of 7Ice sheets

Interglacial
  • Interglacial permanent ice only close to the North and South Poles.
Glacial
  • Glacial ice spreads much further south from the North Pole and further north from the South Pole.
Yuka
  • Yuka a baby mammoth found frozen in Siberia that lived about 39 000 years ago during a colder time.

Part 3 of 7Ice ages

Ice age
Ice age a long cold period containing glacial and interglacial periods.
Earlier times
  • Earlier times there were long warm periods with no permanent ice, even at the poles.
Number
  • Number scientists think there have been several ice ages.
Coldest
  • Coldest the one that began about 850 million years ago, when the Earth may have been covered in ice like a giant snowball.
Today
  • Today the Earth is in an interglacial period within an ice age that has permanent ice at the poles.

Part 4 of 7Evidence of past cold climates

EvidenceWhat it shows
Boulders in unusual placesCarried by ancient glaciers and left when they melted
Scratches on rock surfacesDragged by moving ice
Fossils of cold-adapted animals and plants in warm placesThe climate used to be much colder
Landforms such as U-shaped valleysShaped by glaciers
Ice coresTrapped air bubbles show past carbon dioxide levels and temperature
Tree ringsShow good or poor growth years

Part 5 of 7Pollen evidence from peat bogs

Peat bog
  • Peat bog forms where dead plants decay very slowly because there is little oxygen and the conditions are slightly acid.
Layers
  • Layers the deeper the peat, the older it is.
Auger
  • Auger an instrument used to remove a core of peat, which must be kept in order.
Pollen
  • Pollen identified from different depths to show which plants grew.
Climate
  • Climate worked out because each plant lives in a particular type of climate.

Part 6 of 7Natural causes of climate change

Earth's orbit and tilt
  • Earth's orbit and tilt changes over time.
Sun's output
  • Sun's output changes in energy given out.
Volcanoes
  • Volcanoes large eruptions put dust in the air that reflects sunlight and cools the Earth.
Moving continents
  • Moving continents alter currents and winds.

Part 7 of 7Greenhouse effect and warming

1
Radiation from the Sun passes through the atmosphere.
2
The Earth's surface absorbs it and warms up.
3
The Earth emits infrared radiation.
4
Greenhouse gases absorb some of this and re-emit it, including back to Earth.
5
More greenhouse gases trap more heat and the average temperature rises.
  • Without it
    • the Earth would be about −18 °C.

Key terms

TermMeaning
Glacial periodA very cold period when ice spreads widely.
Interglacial periodA warm period between glacial periods.
Ice ageA long cold period with glacials and interglacials.
GlacierA slow-moving river of ice.
Ice sheetA huge mass of ice covering land.
Peat bogA wet area where dead plants decay slowly.
PollenPowder from flowers used to identify past plants.
Ice coreA sample of ice drilled from deep ice.

Avoid these mistakes

1
Saying the Earth is in a glacial period now — it is in an interglacial period.
2
Saying an ice age is the same as a glacial period.
3
Thinking the climate has never changed naturally.
4
Reading deeper peat as younger — deeper means older.

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