What's covered
Key facts
Earth's atmosphere
Acid rain forms when sulfur dioxide (mainly from burning fossil fuels containing sulfur) dissolves in rainwater to make a weak acid; nitrogen oxides also contribute.
Earth's structure and rocks
Evidence for tectonic plate movement includes matching fossils and rock types on different continents, the fit of coastlines (e.g. Africa and South America), and earthquake/volcano patterns.
Earth's atmosphere
Nitrogen makes up approximately 78% of the Earth's atmosphere.
Earth's structure and rocks
The Earth's core (both outer liquid and inner solid parts) is made mainly of the metals iron and nickel.
Earth's atmosphere
Oxygen makes up approximately 21% of the Earth's atmosphere.
Earth's structure and rocks
Igneous rocks that cool slowly (underground) form large crystals; those that cool quickly (at the surface) form small crystals.
Earth's atmosphere
Human activities (burning fossil fuels, deforestation, agriculture) increase greenhouse gas concentrations, intensifying the greenhouse effect and causing global warming.
Earth's structure and rocks
The Earth has four main layers: crust (thin, outer rock), mantle (solid and semi-molten rock), outer core (liquid metal), and inner core (solid metal).
Earth's atmosphere
Global warming raises sea levels in two ways: melting land ice (glaciers and ice sheets) adds water, and warmer seawater expands (thermal expansion).
Earth's structure and rocks
Igneous rocks form when magma (molten rock) cools and solidifies: inside Earth (intrusive, e.g. granite) or at the surface (extrusive, e.g. basalt).
Practice questions with answers
A taste of the 20 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What gas makes up about 78% of the atmosphere?
- •Argon
- •Carbon dioxide
- ✓Nitrogen
- •Oxygen
What are the three rock types?
- •Hard, soft, medium
- ✓Igneous, sedimentary, metamorphic
- •Limestone, sandstone, clay
- •Volcanic, oceanic, lake
What gas makes up about 21% of the atmosphere?
- •CO₂
- •Helium
- •Nitrogen
- ✓Oxygen
How is igneous rock formed?
- •Heat and pressure change existing rock
- •Layers of sediment compress over time
- ✓Molten rock cools and solidifies
- •Rivers deposit minerals in lakes
Which greenhouse gas is added by burning fossil fuels?
- •Argon gas
- ✓Carbon dioxide
- •Hydrogen gas
- •Nitrogen gas
How is sedimentary rock formed?
- •Heat and pressure transform rock
- ✓Layers of sediment compress over time
- •Molten rock cools quickly
- •Rocks break apart in water
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