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Science 7

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Planet Earth

Ten questions of mixed difficulty, covering Planet Earth. Print it, or work through it on screen — the answer key starts on its own page.

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Planet Earth

Science 7 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. Water seeps into a crack in a boulder, freezes and expands. Over many winters, the boulder splits apart. This is

    1. a) deposition
    2. b) mechanical weathering
    3. c) erosion
    4. d) chemical weathering

  2. Lava pours out of a volcano and cools quickly in the air, forming rock with crystals too small to see. This rock is

    1. a) metamorphic
    2. b) sedimentary
    3. c) extrusive igneous
    4. d) intrusive igneous

  3. A canyon wall shows four flat, undisturbed layers of rock: sandstone on top, then shale, then limestone, then conglomerate at the bottom. Which layer formed first?

    1. a) The limestone
    2. b) The sandstone
    3. c) The shale
    4. d) The conglomerate

  4. A fish dies and sinks to the bottom of a lake. Which is most likely to lead to it becoming a fossil?

    1. a) It is quickly buried by mud, which later hardens into rock
    2. b) It washes up on a beach and dries out in the sun
    3. c) It lies uncovered on the lake bottom for many years
    4. d) Scavengers eat it and scatter its bones along the shore

  5. A tectonic plate moves about 5 cm per year. At that rate, how far does it move in 1 million years?

    1. a) 5 km
    2. b) 500 km
    3. c) 50 m
    4. d) 50 km

  6. Rock high in the Rocky Mountains contains fossils of sea creatures. What is the best explanation?

    1. a) The sea was once deep enough to cover the peaks as they are today
    2. b) Glaciers carried the fossils up from the ocean onto the peaks
    3. c) The rock formed on an ancient sea floor and was later pushed up
    4. d) The creatures lived in high mountain lakes that later dried up

  7. Big Rock, near Okotoks, is a huge boulder sitting alone on flat prairie. It is made of a kind of rock found in the Rocky Mountains, not in the ground around it. How did it most likely get there?

    1. a) A glacier carried it and left it behind when the ice melted
    2. b) The softer rock around it wore away and left it standing
    3. c) A river rolled it across the prairie during a flood
    4. d) A volcano nearby threw it out during an eruption

  8. A geologist finds granite, with large, interlocking crystals, at Earth's surface. Which history best fits this rock?

    1. a) Sand grains were pressed together and cemented into layers on a sea floor
    2. b) Magma cooled slowly on the surface, where the air kept it warm for years
    3. c) Magma cooled slowly deep underground, then the rock above it was worn away
    4. d) Lava cooled quickly at the surface, which gave the crystals time to grow

  9. The Royal Tyrrell Museum is near Drumheller, in the badlands of the Red Deer River valley, where many dinosaur fossils have been found. Why are fossils found there more easily than on most of the flat prairie?

    1. a) The badlands rock is igneous, which preserves bones better than other rock
    2. b) Dinosaurs lived only in the Drumheller area and nowhere else in Alberta
    3. c) Erosion has cut down through the rock, exposing layers from the time of the dinosaurs
    4. d) Glaciers carried the dinosaur bones there from the Rocky Mountains

  10. Two mineral samples both look shiny and gold. Rubbed on an unglazed tile, one leaves a greenish-black streak and the other a golden-yellow streak. What is the best conclusion?

    1. a) They are different minerals, since one must be harder
    2. b) They are the same mineral, but one sample is dirtier
    3. c) They are the same mineral, since they are the same colour
    4. d) They are different minerals, since streak is more reliable than colour

Answer key · Planet Earth

Science 7 · maddyhelps.com

  1. b) mechanical weathering — Freezing water pries the rock apart without changing what it is made of, so this is mechanical weathering. Erosion is the next step, when the broken pieces are carried away by water, wind, ice or gravity.
  2. c) extrusive igneous — Rock that forms when melted rock cools is igneous, and cooling fast at the surface gives crystals no time to grow, which makes extrusive rock such as basalt fine-grained. Intrusive igneous rock, such as granite, cools slowly underground and has large crystals.
  3. d) The conglomerate — Sediment settles one layer on top of another, so in undisturbed layers the lowest was laid down first and the top one last. Reading the wall like a page, from the top down, gives the youngest layer instead of the oldest.
  4. a) It is quickly buried by mud, which later hardens into rock — Quick burial keeps scavengers, decomposers and oxygen away from the remains, and as the mud hardens into sedimentary rock the shape is preserved. Left in the open, a body is eaten or rots away, which is why only a tiny share of living things ever become fossils.
  5. d) 50 km — 5 cm × 1 000 000 = 5 000 000 cm; divide by 100 to get 50 000 m, then by 1000 to get 50 km. The wrong answers all come from losing count of zeros, so change units one step at a time: 100 cm in a metre, 1000 m in a kilometre.
  6. c) The rock formed on an ancient sea floor and was later pushed up — Sediment on an ancient sea floor buried the creatures and hardened into rock, and much later the movement of Earth's plates folded and pushed those layers up into mountains. The land rose; the sea never climbed to the peaks as they stand today.
  7. a) A glacier carried it and left it behind when the ice melted — Glaciers can carry boulders a very long way and drop them where the ice melts; a boulder moved like this is called a glacial erratic. It cannot be left over from worn-away rock, because it is a different kind of rock from the ground it sits on.
  8. c) Magma cooled slowly deep underground, then the rock above it was worn away — Large crystals need slow cooling, which happens deep underground where the surrounding rock keeps the magma hot, so granite is intrusive. For it to be at the surface now, the rock that once covered it must have been worn away by weathering and erosion over a very long time.
  9. c) Erosion has cut down through the rock, exposing layers from the time of the dinosaurs — Across most of the prairie, the dinosaur-age rock lies buried under soil and younger deposits. In the badlands, water has worn the land into steep, bare slopes, so the old layers are exposed and erosion keeps uncovering new bones.
  10. d) They are different minerals, since streak is more reliable than colour — Pyrite, known as fool's gold, looks like gold but leaves a greenish-black streak, while real gold leaves a golden-yellow one. The colour of a sample's surface can vary or fool you, but a mineral's streak, the colour of its powder, stays the same.