P1 The Earth in the Universe

1. P1 The Earth in the Universe

2. Key Facts • The universe is 14,000 million years old • The universe possibly started with a big bang and has been expanding ever since • Our Solar system formed 5,000 million years ago from dust and gas of old stars • The sun is a ball of extremely hot gas, it’s diameter is 109 times larger than the Earth’s • A galaxy is a huge group of stars. Our solar system belongs to the Milky Way galaxy.

3. Earth Crust Only 10-40km deep Mantle Extends half way to it’s centre Core Made mainly of iron Solid at the centre, liquid above

4. Rocks tell Stories! Deeper layers are older layers, younger rocks are usually on top Fossilsin the layers show which species lived when. Many species have become extinct. Cross-cutting features- if one type of rock cuts across another rock type, it is younger e.g. hot magma can fill cracks in existing rocks and solidify as new rock. These clues only tell us which rocks are older than others, not how old the rocks actually are. Some rocks are radioactive, scientists can estimate their age by measuring the radiation given off. This is called radioactive dating.

5. Rock Cycle Erosion Transportation Deposition of sediment Compaction and cementation What do each of these processes mean? There must be movement under the Earth’s surface that changes rocks and lifts land up to build new mountains. Otherwise, erosion would wear the continents flat! Also, the Earth must be older than the oldest rocks found here.

6. Mountains, Volcanoes and Earthquakes. • When 2 plates collide, they crumple up forming mountains. • A volcano is a vent in the Earth’s surface that erupts magma. • Earthquakes occur when 2 plates slide past each other causing rocks to break.

7. Reducing the Damage • Educate people. • Organize public drills. • Building regulations. • Prepare emergency plans and train staff.

8. Continental Drift • Wegner’s theory • All the continents were once a single continent, called Pangaea. • This split up and the continents started moving. • When continents bump into each other they form mountains. • Earthquakes, volcanoes and mountain building generally occur at the edges of tectonic plates; Evidence for this: • Mountain chains match up • Fossils match up • The continents fit together like a jigsaw (not perfect because of erosion of cliffs!)

12. Continental Drift

15. Continental Drift Some did not agree with Wegener because; • The movement is very slow and can not be detected. • Wegener was not a geologist. • Simpler ideas were also suggested

16. Sea Floor Spreading • Sea floor spreading is caused by continents drifting apart forming an oceanic ridge. • They do so at 10cm per year. • Therefore 10cm of rock is produced in the middle of the oceans every year. • These layers of rock become magnetised in the direction of the Earth’s magnetic field. • Periodically, the Earth’s magnetic field is reversed. This causes the rocks at the bottom of the oceans to be magnetised in different directions giving it a ‘striped’ appearance.

18. Why do plates move? • Solid mantle below Earths crust moves slowly, moving plates above. • Mantle moves because of convection currents • Decay of radioactive elements in the Earth’s core releases energy that causes these convection currents.

20. Convection Current

21. Mountain Formation Where two continental plates collide, mountains form.

22. Oceanic Ridge Where two oceanic plates are moving apart and new sea floor is being produced Sea floor spreading is caused by two oceanic plates diverging (moving apart from each other). Magma rises up between the two plates to form new ocean floor (and sometimes volcanoes). Where new oceanic plate is forming is called an oceanic ridge.

23. Seafloor Spreading

24. Magnetic Stripes

25. Why do earthquakes happen?

26. Epicentre of an earthquake

27. The Solar System • Formed over a long period of time, about 5,000 million years ago • Started as clouds of dust and gas which were pulled together by the force of gravity • This created intense heat leading eventually to nuclear fusion- star was born (our sun)

28. The Solar System • This consists of the Sun, the Earth, the moons, the planets, asteroids and comets.

29. Asteroids • Craters are caused by asteroids which collide with other objects in the solar system. • This could cause catastrophic consequences on Earth. • This may have caused a number of extinctions including the dinosaurs.

30. The Sun • The heat and light is caused by nuclear fusion when hydrogen nuclei fuse to form helium. • All elements larger than helium were created in earlier stars. • All stars have a life cycle. • The information we get about other stars comes from radiation that we can detect.

31. Life Cycle of a Star

32. Light • Light travels very fast, 300,000km/s. • That means that objects far away are observed as they were a long time ago. • A light year is the distance travelled in one year. • Measuring distances between stars is difficult because of the vast distances.

33. Measuring Distances • The distance of stars can be measured using either: • Parallax • Brightness

34. Movement of Galaxies • The Sun is a star in the galaxy called The Milky Way. • There are billions of galaxies in the Universe, all moving away from us. • The further they are from us the faster they move away (Hubble’s Law). • This suggests that the Universe is expanding.

35. Fate of the Universe? Universe expands forever. Universe reaches it’s maximum size Universe collapses in a big crunch!

36. Alien Life • There are billions of galaxies with billions of stars, many of which have planets around them. • Some scientists believe that life may exist on some of these. • No evidence of alien life has been detected.

37. Additional Facts • Light pollution interferes with observations of the night sky. • Scientific claims are evaluated by other scientists by a process called ‘peer review.’