P1 EARTH IN UNIVERSE
- Created by: mhamaia21
- Created on: 28-01-15 16:47
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- P1 THE EARTH IN HE UNIVERSE
- Earth
- 4500 million years old, as it is older than the rocks and oldest are 4000 million years old
- Erosion - compacted sediment produced by weathering and erosion, changing a surface.
- Craters -impact craters from meteors, like on the Moon, craters are erased on earth by erosion
- Mountain formation - without new mountains, earth would have eroded down to sealevel
- Folding - a huge force over a long time fold rocks in half
- More evidence from fossils in sedimentary rock layers, show how life evolved
- More evidence from radioactivity in rocks decaying to find out age
- Structure of Earth
- Thin rocky crust
- Thickness varies between 10 and 100km
- Oceanic crust lies beneath oceans
- Continental crust forms continents
- Mantle
- Almost up to halfway to the centre of Earth
- Higher density and different composition to crust
- Very hot but under pressure
- Core
- Over half of Earth's radius
- Made of nickel and iron, liquid outer but solid inner core
- Decay of radioactive elements in core releases energy and keeps it hot.
- Thin rocky crust
- Continental Drift
- Theory proposed by Wegener, he saw a jigsaw between continents and rocks from ranges
- Fossils of same animals on different continents that could not have swam.
- When two continents collided they forced each other upwards to make mountains
- Geologists did not accept because, Wegener was not a geologist, limited evidence, could be explained by an eroded bridge, movement was not detectable
- Seafloor spreading finally convinced the scientific community
- Tectonic plates
- Float on mantle as they are less dense
- Volcanoes, earthquakes and mountains occur at boundaries, tsunamis by coast
- Seafloor spreading
- Mantle is not solid further down from crust, so convection currents can cause magma to rise, currents move solid mantle and tectonic plates
- Magma rises to fill gaps and hardens, forming new oceanic crust and pushing existing floor outwards
- Seafloor spreads a few centimetres a year
- Plate tectonics
- Polarity of Earth's magnetic field changes every million years, combined with seafloor spreading, this produces rocks of alternating polarity
- At destructive boundaries oceanic crust is subducted and molten rock rises to form volcanoes.
- At collision boundaries sedimentary rock is forced up and mountain ranges are formed
- Earthquakes occur from plates sliding against other, pressure building and energy releasing from epicenter in waves
- Rock cycle, old rock destroyed by subduction, igneous formed when magma at surface, collisions produce heat and pressure folding rocks, sedimentary becomes metamorphic.
- Waves from Earthquakes
- Waves can be detected using seismographs on surface
- Primary Wave
- Travel faster than S-waves, can travel through solid and liquid
- Longitudinal waves
- Secondary Wave
- S-waves can only travel through solids
- Transverse waves
- Waves travel faster through higher density rocks
- Change in speed at rock boundaries causes refraction
- Types of wave
- Waves are regular patterns of disturbance that transfer energy from one point to another without moving particles of matter
- Longitudinal
- Particles vibrate back and forth in same plane as direction of wave movement
- Sound travels in this way
- Particles vibrate back and forth in same plane as direction of wave movement
- Transverse
- Particles vibrate up and down perpendicular to direction of wave movement
- Light and water ripples travel in this way, also all electromagnetic waves
- Particles vibrate up and down perpendicular to direction of wave movement
- Wave features
- Amplitude - maximum disturbance caused by a wave
- Wavelength - between corresponding points on adjacent disturbances
- Frequency - waves in one second
- Wave speed and frequency
- Constant speed - increase frequency, decreases wavelength
- Constant frequency - increase wave speed, increases wavelength
- Speed of wave is usually independent of its frequency and amplitude
- Solar System
- Formed 5000 million years ago, started as dust and gas clouds pulled together by gravity, creating intense heat, nuclear fusion began creating Sun, left over dust and gas formed smaller masses attracted to Sun
- 8 planets orbiting Sun, moons orbiting planets, asteroids orbiting Sun, cometsorbiting Sun, dwarf planets, orbiting Sun
- Planets, moons and asteroids move in elliptical orbits, comets in highly elliptical orbits
- Sun
- 500 million years older than earth
- Energy comes from fusion of hydrogen that produces atoms of larger mass, binding energy of hydrogen atoms is released
- All elements larger than helium formed by fusion in earlier stars
- Nuclei of atoms fuse
- Speed of Light
- Finite, 300,000km/s, sunlight takes 8 minutes to reach Earth
- One light year is the distance light travels in one year, 9500 billion km
- Measuring distance in Space
- Relative brightness
- Dimmer means further away, however brightness can vary from star to star
- Parallax
- Stars in near distance appear to move against background of distant stars, closer stars move more, the further the star the less accurate the measurement
- Relative brightness
- Other Galaxies
- If source of light is moving away, wavelengths are longer than if stationary
- Wavelengths of nearby galaxies are longer than expected, so galaxies are moving away
- Hubble's Law : Speed at which a galaxy moves away is proportional to its distance from us.
- Evidence that the Universe is expanding
- If electromagnetic waves are longer, it has been red shifted, so object is moving away from us, more red shifted the faster moving it is
- The Beginning and the End
- The big bang 14 000 million years ago
- Future hard to predict due to difficulty measuring large distances and motion of very distant objects
- Not enough mass, the Universe will continue expanding, too much mass and gravity willpull everything together, Universe will collapse
- Earth
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