Fast and slow Earth changes · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Fast and slow Earth changes

Science · Space Systems & Earth's History · ages 7-8
Name ______________________   Date ____________

  1. Which example describes a slow Earth change?

    • Lava starts flowing out of a volcano in minutes
    • A mountain range grows over millions of years
    • A landslide moves loose rocks downhill in seconds

  2. Which event can shake the ground within seconds?

    • Earthquake shaking
    • Canyon carving
    • Mountain-range growth

  3. Lava can start flowing from a volcano within minutes.

    Circle one:   True   False

  4. A 15-second time-lapse clip shows a hillside changing. What must you check before deciding whether the land changed quickly?

    • The real time covered by the recording
    • The number of times the clip was played
    • The length of the clip on the screen

  5. A river has been cutting into rock for thousands of years, making a deep canyon. Is this a fast change or a slow change?

    • Fast change
    • Slow change
    • Not a change at all

  6. Which record best supports gradual growth of a mountain range?

    • A film records a minute of earthquake shaking
    • Dated height readings show small rises over 100 years
    • A close-up photo shows lava flowing down the side of a volcano

  7. A scientist photographs a canyon in year one. She takes another photo 10 years later, then one more photo 10 years after that. How many years passed between the first and last photo?

    Answer: ______________

  8. Two photos taken 30 years apart show that rocks fell from a cliff between the photo dates. Leo says the fall must have lasted all 30 years. Which conclusion fits the evidence?

    • The rock fall lasted for the whole gap between photos
    • The rock fall happened on the day of the later photo
    • These photos leave the speed of the rock fall unknown
LightMySky · lightmysky.comW1-mt_ZJu8s-Q1xa-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Fast and slow Earth changes W1-mt_ZJu8s-Q1xa-s1

  1. A mountain range grows over millions of years · Growth over millions of years is gradual. The other examples describe changes happening in minutes or seconds.
  2. Earthquake shaking · Earthquake shaking can happen within seconds. Long-term canyon carving and mountain-range growth take much longer.
  3. True · Lava can start flowing rapidly even when an eruption continues much longer.
  4. The real time covered by the recording · Time-lapse speeds up events. The 15-second clip length does not tell us how much real time the hillside change took.
  5. Slow change · The prompt says canyon carving took thousands of years. That long total duration makes this a slow change; it does not tell us how much rock moved during each event.
  6. Dated height readings show small rises over 100 years · Small measured rises across 100 years support gradual growth during that period.
  7. 20 · There are two separate 10-year gaps. 10 + 10 = 20 years between the first and last photo.
  8. These photos leave the speed of the rock fall unknown · The photos show that rocks fell between two dates. They do not show when the fall began or how long it lasted, so the 30-year photo gap does not establish its speed.
Worksheet · LightMySky