Grade 7 · Science · Unit 5 of 6
Restless Earth
Plates, quakes and deep time
What your child practises
Earth's layers, plate tectonics, earthquakes and volcanoes, fossils in rock layers, and the order of major events in Earth's 4.6-billion-year history. Includes how First Nations oral histories and scientific evidence together date the great 1700 earthquake.
Yukon Curriculum learning standard: Layers of the Earth; plate tectonics; earthquakes and volcanoes; fossils and geological time; First Peoples knowledge of Earth's history
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Put these events in Earth's history in order, oldest first.
- 🐟First fish swim in the oceans
- 🦠First simple life appears in the oceans
- 🧍Modern humans appear in Africa
- ☄️Dinosaurs (except birds) die out
First simple life appears in the oceans → First fish swim in the oceans → Dinosaurs (except birds) die out → Modern humans appear in Africa
Hint: First simple life appears in the oceans: at least 3.5 billion years ago. First fish swim in the oceans: about 500 million years ago. Dinosaurs (except birds) die out: about 66 million years ago. Modern humans appear in Africa: about 300,000 years ago.
Question 2
Which fossil is probably the oldest?
Fossils in undisturbed rock layers at a cliff Layer Fossil found 1 (top) mammoth tooth 2 dinosaur bone 3 ammonite shell 4 (bottom) trilobite - trilobite
- dinosaur bone
- mammoth tooth
- ammonite shell
trilobite
Hint: Rock layers form on top of each other, so in undisturbed rock the bottom layer is oldest and the top layer is youngest. This is called the law of superposition.
Question 3
What are tectonic plates?
- Flat rocks found only on beaches
- Huge slabs of Earth's crust and upper mantle that slowly move
- Layers of ice on the poles
- Clouds of gas in the atmosphere
Huge slabs of Earth's crust and upper mantle that slowly move
Hint: Earth's outer shell is broken into giant pieces that move a few centimetres a year.
Question 4
The inner core is hotter than the surface of the Sun. Why is it solid?
- It gets no heat from anywhere
- The enormous pressure squeezes it into a solid
- It is cooled by the oceans
- It is made of ice
The enormous pressure squeezes it into a solid
Hint: The weight of all the rock above presses so hard that the iron can't melt.
Question 5
Which layer of Earth is made of liquid metal?
- the outer core
- the inner core
- the mantle
- the crust
the outer core
Hint: The outer core is liquid iron and nickel. Its swirling motion creates Earth's magnetic field.
Question 6
About how old do scientists estimate Earth to be?
- about 460,000 years
- about 46 million years
- about 4.6 billion years
- about 46 billion years
about 4.6 billion years
Hint: Scientists date the oldest rocks and meteorites using radioactive elements. Earth is a few billion years old.