Ontario Grade 12 SES4U Earth and Space Science (Grade 12, University Preparation)
Chapters: 6
1. A. Scientific Investigation Skills and Career Exploration
A1 Scientific Investigation Skills · A2 Career Exploration
- The Scientific Method – The scientific method is the careful way scientists find out how the world works. Observe something, ask a testable question, make a hypothesis (a clear, testable guess), test it with a fair experiment (change one variable, measure one, keep the rest the same), repeat and record data, analyse it, draw a conclusion and share it so others can check. Results that fail the test are useful too: they send you back to a new hypothesis.
2. B. Astronomy (Science of the Universe)
B1 Relating Science to Technology, Society, and the Environment · B2 Developing Skills of Investigation and Communication · B3 Understanding Basic Concepts
- Stars and Galaxies: From Starlight to the Big Bang – Everything we know about stars comes from their light. Splitting starlight into a spectrum shows dark lines that tell us which elements a star has; the colour tells us its temperature (blue = hot, red = cool) and stars are sorted into classes O B A F G K M. The H-R diagram plots true brightness against temperature: most stars, including the Sun, lie on the main sequence, with giants top right and white dwarfs bottom left. A star is born in a nebula and its mass decides its life: a Sun-like star becomes a red giant and then a white dwarf; a star of more than about 8 solar masses becomes a supergiant, explodes as a supernova and leaves a neutron star or black hole. Stars gather in galaxies, which are spiral, elliptical or irregular. Distances are huge, so we use the astronomical unit, the light-year and the parsec. Galaxies are moving apart, faster when farther (Hubble's law), which together with the cosmic microwave background supports the Big Bang about 13.8 billion years ago.
3. C. Planetary Science (Science of the Solar System)
C1 Relating Science to Technology, Society, and the Environment · C2 Developing Skills of Investigation and Communication · C3 Understanding Basic Concepts
- The Solar System – The Solar System is the Sun and everything its gravity holds: 8 planets, their moons, dwarf planets, asteroids, comets and dust. The inner four planets (Mercury, Venus, Earth, Mars) are small and rocky. After the asteroid belt come the giants: gas giants Jupiter and Saturn, ice giants Uranus and Neptune. Gravity pulls planets towards the Sun while they move sideways, so they travel in orbits; closer planets move faster and have shorter years. It all formed about 4.6 billion years ago from a spinning cloud of gas and dust.
4. D. Recording Earth’s Geological History
D1 Relating Science to Technology, Society, and the Environment · D2 Developing Skills of Investigation and Communication · D3 Understanding Basic Concepts
- Climate Change and the Greenhouse Effect – Climate is the average weather of a place over about 30 years. Greenhouse gases like carbon dioxide and methane trap some of the heat the Earth gives off. Humans have added a lot more of these gases by burning fossil fuels and cutting forests, so the Earth is warming. This causes melting ice, rising seas and more extreme weather. We can cut emissions (mitigation) and prepare for changes (adaptation).
- Radiometric Dating – Relative dating puts rocks and fossils in order (lower layers are usually older). Absolute (radiometric) dating gives an age in years. A rock crystal traps radioactive parent atoms that decay at a fixed rate into daughter atoms. After each half-life, half of the parent atoms are left. Measuring the daughter-to-parent ratio gives the age: t = T½ × log₂(1 + D/P).
5. E. Earth Materials
E1 Relating Science to Technology, Society, and the Environment · E2 Developing Skills of Investigation and Communication · E3 Understanding Basic Concepts
- Environmental Stewardship: Caring for the Planet as We Use Technology – Environmental stewardship means using the Earth's resources carefully so they last, and fixing harm where we can. Every product, from a phone to a hospital machine, has a life cycle: raw materials, making, transport, use and end of life. Each stage uses energy and makes waste. Good stewards keep products longer, choose efficient machines, follow the waste hierarchy (refuse, reduce, reuse, recycle, then dispose), send e-waste to proper recyclers and support laws and company practices that protect nature. Technology can harm the environment, but it can also help: solar panels, LEDs and smart sensors cut waste.
- Rocks and Minerals – A mineral is a natural, non-living solid with a fixed chemical make-up and a regular crystal shape, like quartz or halite. A rock is a mixture of one or more minerals. Rocks are of three types: igneous (from cooled magma or lava), sedimentary (from layers of pressed bits) and metamorphic (changed by heat and pressure). The rock cycle slowly turns each type into the others over millions of years.
6. F. Geological Processes
F1 Relating Science to Technology, Society, and the Environment · F2 Developing Skills of Investigation and Communication · F3 Understanding Basic Concepts
- Distribution of Oceans and Continents: Drift, Spreading and Plates – In 1912 Alfred Wegener said all continents were once one landmass, Pangaea, surrounded by one ocean, Panthalassa, and that they drifted apart. Matching coastlines, rocks, fossils, glacier deposits and placer gold supported him, but he could not explain the force. Mapping the ocean floor showed ridges, plains and trenches; Harry Hess then proposed sea-floor spreading: new crust forms at mid-ocean ridges and old crust sinks at trenches. This led to plate tectonics: the lithosphere is broken into rigid plates that move on the soft asthenosphere and meet at divergent, convergent and transform boundaries. The Indian plate broke away from the south, moved north, and collided with Asia to raise the Himalayas.