# Earth and Space

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Earth and Space

## 1. The Universe

### 1.1. The Night Sky

1.1.1. For years people believed that the earth was the centre of the universe, until Ptolemy, a Greek astronomer, proposed a geocentric model of the Universe in the 2nd century A.D. His model postulated that: THE stars were located on a large outer sphere and rotated rapidly, THE planets were each on smaller inner circular orbits; THE Sun revolved around the Earth on the 4th orbital circle from Earth.

1.1.2. In order to locate stars in the night skies more efficiently astronomers use something called the CELESTIAL SPHERE. The Celestial Sphere is a dome that surrounds the Earth. It is divided very similar to Earth with the North and South celestial poles as an extension of the Earth’s axis. The celestial equator is a projection of Earth’s equator onto the sphere. Astronomers use 2 different coordinate systems similar to the latitude-longitude system used on Earth to locate stars in the sky: RIGHT ASCENSION-DECLINATION - Right Ascension is analogous to longitude and is measured in hours, minutes, and seconds, from the point of vernal equinox. Declination is analogous to latitude and is measured in degrees from the celestial equator. NOTE: 1 hour = 15° of arc (1° arc is equivalent 1° of longitude) and 1 minute = 1/60° of arc EXAMPLE: Proxima Centauri has a declination of -62°40’ (the negative indicates it is located 62° below the celestial equator) and a right ascension of 14h 29.7m. ALTITUDE-AZIMUTH - Altitude is the angular distance, measured from 0 to 90 degrees, of a celestial object above the observer’s horizon. Azimuth is the compass angle from due N to the location of the celestial object.

1.1.3. CIRCUMPOLAR STARS are the stars closest to Polaris do not set beneath the horizon, and are called circumpolar stars.

1.1.4. ASTERISMS AND CONSTELLATIONS Constellation patterns have been found on tablets over 4 000 years old in the Euphrates River Valley. A group of stars may appear to be connected, however they are usually far apart. An asterism is a group of recognizable stars that is not recognized as an official constellation. An area in the sky defines a constellation. A constellation will often contain an asterism within its area, for example the big dipper is a part of the constellation Ursa Major.

1.1.5. SEASONAL PATTERNS Although some of the circumpolar constellations (for example Ursa Major and Ursa Minor) are visible all year round, others (for example Orion-WINTER and Cygnus-SUMMER) are only visible at certain times of the year.

### 1.2. Classifying and Measuring Stars

1.2.1. SPECTROSCOPY When the visible light from the stars goes through a prism it produces a spectrum, each spectra is unique as is determines the element's motion, temperature, composition, and density.

1.2.2. ELECTROMAGNETIC SPECTRUM The types of waves that go in order of shortest wavelength to longest wavelength is Gamma Rays, X-Rays, Ultra-violet, Visible light (ROYGBIV), Infrared and then Radio Waves.

1.2.3. PROPERTIES OF STARS Composition of a Star - The unique patterns of bands found in elements can match those of emission spectrum in stars. Finding matching bands can determine the elements present in the star. Motion of a Star - When a star is moving to/away from Earth, a shift in emission/absorption lines is visible. Away from Earth = longer wavelengths (Redshift), to Earth = shorter wavelengths (Blueshift). Atmosphere of a star - When emission spectra lines are smeared, the star has a high atmospheric density, narrow lines mean the star has low atmospheric density. Colour - “Cool” stars are red, hotter are blue. Temperature of a Star - Temperature and/or maximum wavelength can be found using the formula λmax = 0.0029/T

1.2.4. Other properties include: Apparent Magnitude (how bright from Earth), Absolute Magnitude (how bright from 32.6 light years), Luminosity (Energy output in Watts), Distance (measuring parallax), Radius (Determined by temp & luminosity) and Mass (Found through gravitational forces and nearby star interactions.

1.2.5. SPECTRAL CLASSIFICATION Stars can be classified into one of 7 classes: O - (Blue, 28k-50k K, Helium & Weak Hydrogen) B - (Blue-white, 10k-28k K, strong Helium, weak Hydrogen and Calcium) A - (White, 7.5k - 10k K, strong hydrogen and small strong calcium) F - (White-Yellow, 6k - 7.5k K, dark lines of calcium and hydrogen) G - (Yellow, 4.9k - 6k K, Calcium strong, neutral hydrogen lines weak) K - (Orange, 3.5k - 4.9k K, strong calcium lines, neutral metal lines) M - (Red, 2k-3.5k K, strong lines for neutral atoms, titanium oxide)

### 1.3. Stellar Evolution

1.3.1. HERTZSPRUNG-RUSSELL DIAGRAM The life of a star can be determined by observing the Hertzsprung-Russell diagram, they developed the diagram by plotting the luminosity on the y-axis and temperature on the x-axis. If the location is known on the Hertzsprung-Russell diagram then the luminosity, spectral class, absolute magnitude, and temperature can all be determined by reading the values from the axis. Stars placed at the top are the giant and supergiants, stars found in the bottom left are classified as white dwarfs and within a band that runs from the upper left to the lower right corner of the graph called the main sequence is where 90% of stars can be found.

1.3.2. STAR BIRTH: 1. The birth of a star begins with a cloud of gas and dust called a nebula. 2. The dust and gas begin to condense and the particles move closer due to gravitational forces. 3. As the dust-gas cloud gets smaller it begins to rotate and the temperature increases as the density of the star increases. 4. Once the temperature of the “protostar” reaches 10 000 000°C a fusion reaction begins, converting hydrogen to helium and releasing energy, and the Star “turns on”.

1.3.3. LIFE CYCLE OF A STAR (Average Mass) Lifespan of 10 billion years. RED GIANT - Once all of the hydrogen turns into helium the gravitational forces cause the helium core to collapse, the star then becomes hot enough to turn into carbon. The outer layers expand and cool, Red Giant phase is 100 million years. PLANETARY NEBULA - When helium fusion stops, the star expands again, loosing lots of mass. WHITE DWARF - Eventually the hot core will cool and leave a dim white dwarf star. Then cools to possibly form a black dwarf. (Massive) Lifespan of 10 million years. RED SUPERGIANT - In massive stars, carbon fusion can start, forming silicon and iron. Outer layers are now made of hydrogen and helium. Inner layers are heavier and heavier, till full iron core. SUPERNOVA - Iron can't be fused into heavier elements and therefore, no more outward energy pressure from the core. A second later, gravity makes the star collapse, temperature rises to over 100 billion degrees and iron atoms are crushed. Core becomes solely neutrons instead of protons and electrons. The core now recoils, releasing a lot of energy. There are two possible outcomes after the supernova: NEUTRON STAR - The remaining neutron star may be only 20 km in diameter but be 3 trillion times denser than the Sun. Producing strong magnetic fields, and electrical charges. BLACK HOLE - If the star is 15 solar masses or greater the gravitational force is so great that light can't escape.

### 1.4. Star Distances

1.4.1. THERE ARE 5 METHODS OF CALCULATION STAR DISTANCES RADAR - Using electromagnetic waves in radio wavelengths, we can determine the distance by the speed of the beam (time it takes for the beam to hit the star and come back). PARALLAX - Displacement of a star between two different lines of sight, measured with d=1/p (d = distance in parsecs, p = angle in arcsec (1/3600 of a degree)). ABSOLUTE/APPARENT MAGNITUDE - Using the brightness of a star to determine the distance (d = 10 (m-M+5)/5, d = distance in parsecs, m = apparent magnitude, M = absolute magnitude). CEPHEID VARIABLES - Much like absolute and apparent magnitude, variable stars distance is found through how much light is emitted. TYPE IA SUPERNOVAE - When explode, emit same amount of light, so again observing apparent/absolute magnitude can be used to find distance.

### 1.5. Big Bang and Galaxies

1.5.1. THE BIG BANG THEORY the currently accepted model for the formation of the universe. THE Big Bang did not occur from a single point in space. THE Big Bang occurred about 14 billion years ago and all matter was in a super hot dense state. THE matter expanded and cooled slowly. AFTER 10-4 seconds, matter cooled enough to form protons and neutrons. AFTER ½ million years electrons combined with nuclei to form neutral hydrogen atoms. AFTER a billion years galaxies and stars began to form. ORIGINAL stars consisted of mostly hydrogen. AS the universe expands galaxies move apart.

1.5.2. GALAXIES Edwin Hubble classified galaxies based on the following criteria: SOME galaxies had arms of dust and gas that appeared in a spiral pattern (S). The arms on the spiral galaxies were wound more tightly (Sa) than for other spiral galaxies (Sb, Sc). (The letters a, b, and c refer to how tight the arms are with “a” being the tightest.) HUBBLE noticed that some of the spiral galaxies had bright bars going through the centre and he divided the barred spiral class (SB) from the spiral class. (The letters a, b, and c are also used to determine how tightly wound the barred spiral arms are.) ELLIPTICAL galaxies varied from nearly circular (E0) to highly elliptical (E7). THERE were other galaxies that did not fit into either of the above galaxies; these were called irregular galaxies (Irr). HE also found some unusually shaped galaxies called peculiar galaxies. These galaxies are actually the interaction or collision of two or more galaxies causing their shapes to be distorted.

## 2. The Solar System

### 2.1. Structure of the Solar System

2.1.1. THE SUN It’s at the center of the solar system, energy made by fusion of hydrogen - helium.

2.1.2. PLANETS The eight planets rotate counter clockwise around the sun, with their orbital planes being closely aligned with the Sun’s equator. Mercury, Venus, Earth and Mars are all terrestrial planets (Heavier elements). Jupiter, Saturn, Uranus and Neptune are gaseous planets (Hydrogen and helium, lighter) all having planetary rings.

2.1.3. DWARF PLANETS A smaller planet that lacks technical definitions to be considered one.

2.1.4. SMALL SOLAR SYSTEM BODIES Asteroids - Rocks/metals in asteroid belt near Mars and Jupiter. Meteorites - Smaller asteroids, less than 10m in diameter. Comets - Made of ice

### 2.2. Formation of the Solar System

2.2.1. SOLAR NEBULA THEORY Before a star forms, it contracts due to the gravity that the materials put on each other, so as the masses clump together, becoming bigger and bigger, the attraction to more material gets bigger as well. This core increases in size/density forming a protosun. The protosun doesn’t create energy with fusion of hydrogen yet as it still is collecting mass, this collection stops when the dense core reaches a few million Kelvin, forming a star. As it turns into a star is spins counter-clockwise and increases in speed as it becomes smaller and smaller.

### 2.3. Solar System Geology

2.3.1. MAJOR GEOLOGICAL PROCESSES The following are found on Earth and other planets producing unique landforms. Gradation - Erosion, transportation and deposition of surface materials. Impact Cratering - Occurs when space material (Asteroids, comets) hit the surface. Tectonism - Movement of rock due to plate movements, fractures and faulting. Volcanism - Produces volcanoes and distinct lava flows.

### 2.4. Planetary Motion

2.4.1. KEPLER’S 1ST LAW Orbits are elliptical and Sun is at one focus.

2.4.2. KEPLER’S 2ND LAW The planets sweep out equal areas in an equal amount of time.

2.4.3. KEPLER’S 3RD LAW The motions of moons around a planet are the same as the motions of planets around the Sun.

### 2.5. Impact on Earth

2.5.1. THE SUN AND MOON Gravitational pull of these on Earth create the low and high tides, literally pulling up the water as the moon goes around the Earth

### 2.6. Is there Life out there?

2.6.1. HABITABLE ZONE (HZ) Most important part for survival of life is water, where biochemical reactions occur, and much more. A star’s HZ can be determined from its luminosity and temperature. The boundary of the HZ is at 1.35 AU, although due to evidence through a Martian meteorite, this boundary was at some point 1.55 AU. Still, the general characteristics for a Habitable Zone is between 0°C and 100°C and water.

2.6.1.1. RANGE OF HZ DEPENDS ON THE STAR Hotter stars have HZs farther out, so an Earth sized planet with a hotter sun would have to be farther, while the same hotter sun for a dwarf planet could be closer to the sun.

2.6.2. HOW MANY TECHNOLOGICAL CIVILIZATIONS ARE OUT THERE? Frank Drake figured a formula to determine the number of communicative civilizations that humans may be able to contact (N = (R* )(fp )(ne )(fl )(fi )(fc )(L)). The number calculated was found to be 50. Although many scientists don’t find this “very good science” so it’s often dismissed.

2.6.3. FERMI PARADOX “If there are extraterrestrials, where are they?” Zoo hypothesis - They don’t want to communicate, they observe us like we do animals in a zoo. Doomsday theory - Intellectual races tend to destroy themselves before they can develop technology to be a space faring species. The great filter - one of a series of steps in the formation of life is interrupted preventing an explosion in colonization. Rare Earth hypothesis – intellectual races do not exist or are extremely rare.

2.6.4. CURRENT STUDIES IN THE SEARCH OF LIFE Mars - Abundance of water, many lakes and small oceans, although now frozen at the poles. Europa - It is currently theorized that the one of Jupiter’s moons, Europa, could be sitting on a large quantity of water. Enceladus - Saturn’s moon was thought to potentially also have water located on it, as a cloud of gas was discovered with tiny grains of ice inside. Titan - Another one of Saturn’s moons, many small bodies of lakes/rivers of liquid bodies. Gliese 581 - Although located far away, it has been calculated that this planet would be in a habitable zone capable of being home to water at a reasonable temperature. HD69830 - Same as Gliese 581, although farther away.

## 3. Earth Materials

### 3.1. Minerals

3.1.1. The Earth's crust is made up of 74.3% Oxygen and Silicon (silicates).

3.1.2. CRYSTAL FORMATION AND STRUCTURE Formed from magma, atoms and ions come together forming bonds in different compounds. Clear crystals can be seen when formed in open spaces, while smooth crystal faces aren’t produced when formed in a confined space.

3.1.3. MINERAL CRYSTAL SHAPES Cubic - All 3 axis same length, meet at 90° (Halite). Tetragonal - 3 axis meet at 90°, but two are same length (Wulfenite). Orthorhombic - 3 axis meet at 90°, all diff. length (Topaz). Monoclinic - 3 axis of different lengths, 2 meet at 90°, the third oblique (Gypsum). Triclinic - 3 axis of different lengths, all oblique (Kyanite). Hexagonal - 3 axis of equal length, 60°, 4th axis is vertical and different length (Quartz).

### 3.2. Mineral Identification

3.2.1. MINERAL FAMILIES Silicates - Non-ferromagnesian silicates (minerals of silicon, oxygen and other elements(Quartz)), and Ferromagnesian silicates (minerals of silicon, oxygen and iron/magnesium(Olivine)). Carbonates - Common, composed of negatively charged carbonate ion bonded to positive metal ion (Calcite). Oxides - Iron combined with oxygen (Limonite). Sulfides - Iron combined with sulphur (Galena). Sulphates - Negative sulphate ion and positive metal ion (Gypsum). Halides - Fluorine or chlorine combined with a positive metal ion (Halite). Phosphates - Phosphate ion combines with a positive metal ion (Apatite). Native Elements - Elements occurring naturally within 5 properties defining a mineral (Copper).

3.2.2. HOW TO DISTINGUISH Colour, streak, lustre, appearance, magnetic properties, cleavage, reaction to acid, specific gravity (density) and hardness.

### 3.3. Rock Cycle and Igneous Rock

3.3.1. ROCK CYCLE All rock types can form each other in one way or another Igneous can be broken down into sediments, forming sedimentary rock through weathering and erosion Igneous can be heated or pressurized into metamorphic rock Metamorphic rock can be broken down into sediments, forming sedimentary rock through weathering and erosion Metamorphic rock can be melted to form magma, and cools to form igneous rock Sedimentary can be heated and pressurized to metamorphic rock Sedimentary can’t turn to igneous without turning into metamorphic first

3.3.2. IGNEOUS ROCK Two types, Intrusive (Plutonic) and Extrusive (Volcanic). Intrusive - magma cooled under Earth’s surface (allows growing minerals & forms large crystals). Extrusive - magma cooled above Earth’s surface (forms small crystals and forms volcanic glass).

### 3.4. Sedimentary Rock

3.4.1. SEDIMENTARY ROCK Three types, Clastic, Chemical or Organic. Clastic - Made of pieces of other rocks loosened by weather transported deeply, compacted and cemented forming sedimentary rock (Texture is sorted grains). Chemical - Water travelling through rock dissolves some elements causing water to become oversaturated (Texture is not sorted grains and layers, small crystals). Organic - Forms from once-living organisms (Texture is observation of marine fossils).

### 3.5. Metamorphic Rock

3.5.1. METAMORPHIC ROCK When rocks are under a lot of heat, pressure or are around mineral-rich fluids, or a combination of all, metamorphic rocks are formed (Heated, foliation or nonfoliated).

## 4. Earth History

### 4.1. Geologic Time

4.1.1. Geological Time Scale The ages given are in millions of years before the present abbreviated as mya. The geologic time scale is divided into four eons. Precambrian time is composed of three eons. The Hadean began 4550mya, the Archean eon 3800mya, and the Proterozoic eon began 2500mya. The current Phanerozoic eon began 570mya. The current eon is divided into eras and periods. The Paleozoic era began 570mya and ended 245mya. The periods of the Paleozoic era with the beginning dates are, Cambrian 570mya, Ordovician 505mya, Silurian 436mya, Devonian 406mya, Mississipian 360mya, Pennsylvanian 320mya, and the Permian 286mya. The Mesozoic era began 245mya and ended 66.4mya. The three periods and start dates are the Triassic 245mya, Jurassic 206mya, and Cretaceous 144mya. The Cenozoic era began 66.4mya and is still going on. The Tertiary period has been recently divided into two different periods. The Paleogene began 66.4mya, and the Neogene 23.7mya, the final period is the Quaternary, which began 1.6mya. The epochs of the Tertiary period are the Paleocene 66.4mya, Eocene 57.8mya, Oligocene 36.6mya, Miocene 23.7mya, and the Pliocene 5.3mya. The Quaternary period is divided into two epochs the Pleistocene 1.6mya and the Holocene 0.01mya.

### 4.2. Fossil Evidence

4.2.1. Fossils are important as they have many uses such as, understanding the evolutionary history of a species, determining the age of rock layers, studying paleoenvironment, studying paleoecology, studying paleogeography and studying paleoclimate.

4.2.2. TYPES OF FOSSILS Original Remains - Whole organisms can be viewed from frozen remains, trapped in tar pits or in a resin material (amber). Casts and Molds - Formed from hard shelled organisms when buried under soft ground. When the ground hardens and the shell decays, an imprint/mold of the organism is left behind. When filled with minerals, a cast fossil is produced. Carbonization - When organisms are buried under high temperature, liquids escape, are forced out of the organism, leaving a carbon silhouette. Permineralization - When an organism is buried, mineral groundwater fill the empty spaces in the organism, the minerals then precipitate, creating a copy made of minerals. Trace Fossil - May include, footprints, burrows, or bite marks.

4.2.3. MASS EXTINCTIONS Fossil records show extinction events, these extinction events are used by scientists to divide the geologic time scale to different units (Over 23 mass extinctions in history).

4.2.3.1. K-T BOUNDARY A period of time during the Cretaceous period when the Chicxulub asteroid had impact sending mass amounts of dust into the air, killing off many planets, and in turn killing off many animal species.

### 4.3. Relative Dating

4.3.1. Stratigraphy is the branch of geology that studies the layers of rock in which events of formation were placed in order of their occurrence. This method of dating is called relative dating and is based on a few principles:

4.3.1.1. Principle of Superposition: states that for an undisturbed layer of rocks the oldest rocks were deposited first and are located on the bottom of the sequence, with each successive layer on top being younger than the one beneath it. In the profile above, layer A was deposited first and is older than layer B. Similarly layer B is older than layer C.

4.3.1.2. Principle of Original Horizontality: states that as the sediments and layers are produced, gravitational forces will deposit the bed horizontal to the surface. Movements of the Earth’s crust have disturbed the strata or layers that are not horizontal. All of the layers in the diagram above are horizontal to the surface and therefore they have not been disturbed.

4.3.1.3. Principle of Cross Cutting: states that any rock intrusions or faults are always younger than the surrounding layers. The surrounding layers had to have been there in order for the fault or intrusion to occur. The fault (E) cuts through layers A, B, and C and therefore it occurred after layer C was deposited. The fault however is older than layer D.

4.3.1.4. Principle of Original Continuity: states that the beds can be traced over a long distance if rock layers are separated by a large basin. A similarity of rock types and fossils demonstrates that the layers are approximately the same age.

4.3.1.5. Principle of Faunal Succession: the evolution and extinction of life over time has produced distinct fossils for different time periods. The age of the rock can then be determined based on the composition of fossils.

### 4.4. Absolute Dating

4.4.1. ATOMIC STRUCTURE Three types of decay: Alpha Decay - An alpha particle, made of 2 protons and neutrons, is emitted. Beta Decay - A neutron breaks apart to form a proton and electron, electron is emitted. Electron Capture - A proton captures an electron and becomes a neutron.

4.4.2. ISOTOPES USED IN RADIOMETRIC DATING Carbon 14 - Nitrogen 14: When an organism dies, organism stops taking in Carbon and the remaining Carbon 14 will decay into Nitrogen 14. The ratio of remaining Carbon 12 to Carbon 14 can determine the age of the plant/animal. Half life of C-14 is 5730, effective dating range of 100-70,000 years. Uranium 238 - Lead 238: Used to date rocks with Zircon mineral, half life is 4.5 billion years, effective dating range of 10 million to 4.6 billion years. Potassium 40 - Argon 40: Used to date many igneous rocks, half life is 1.3 billion years, effective dating range of 50,000 to 4.6 billion years. Rubidium 87 - Strontium 87: Used to date most igneous rocks,half life is 47 billion years, effective dating range from 10 million to 4.6 billion years.

### 4.5. Paleoclimate and its Impacts

4.5.1. PALEOCLIMATOLOGY Paleoclimates can be measured through Ice (pollen within the ice traces back to the amount of precipitation and types of plants), Dendroclimatology (analysis of tree rings), and Fossils and living Organisms (similar to tree rings).

4.5.2. CLIMATE OVER EARTH’S TIMELINE Earth’s Dynamic Climate - Our present climate Precambrian Climate - Harsh climate, acidic rains fell, much warmer, ended with being frozen over. Paleozoic Climate - Glaciation occurred about 430 million years ago lasting a few million years, ice sheet was the size of Antartica, covered what we now know as North Africa. Mesozoic Climate - Fairly warm, although dramatic cooling near the end due to massive asteroid and extensive volcanism, all of which blocked out the sun with debris most likely, cooling the planet. Cenozoic Climate - Relatively cool compared to past eras.

4.5.3. TECTONIC THEORY “The continents were once on large landmass, a supercontinent called Pangaea,” claimed Alfred Wegener in 1912.

4.5.4. MILANKOVITCH CYCLES Three cyclical movements relating to Earth orbiting around the Sun (Eccentricity, Axial Tilt, and Precession).

4.5.5. EARTH’S DYNAMIC ATMOSPHERE Decrease in Carbon Dioxide - When this occurs the Earth cools, 100 million years ago when cyanobacteria evolved gaining the ability to convert carbon dioxide into oxygen, the greenhouse effect was lowered and global temperatures lowered as well. Increase in Carbon Dioxide - When this occurs the Earth warms, Volcanic eruptions in the Permian period raised carbon dioxide levels, increasing the greenhouse effect.

## 5. Geologic Processes

### 5.1. Plate Tectonics

5.1.1. Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core.

5.1.2. THERE ARE 2 TYPES OF PLATE BOUNDARIES Divergent Boundary: Regions where two tectonic plates move apart, causing magma to go through the cracks and form a new crust. Most known is the mid-Atlantic ridge, spreading rate of this ridge is 2 cm/year. Convergent Boundary: Oceanic and continental plates converge, the continental plates moves over the oceanic plate, causing the continental plate to move up forming a mountain chain the surface. As the oceanic crust melts and moves lower into the Earth, molten rock rises and forms volcanoes in the same spots. These are known as subduction zones (oceanic plate subducts under the continental plate). Two oceanic plates converge, same thing happens, but instead form deep trenches Two continental plates converge, but neither subducts, instead the rocks buckle and are pushed upwards. An example of this is the Indian and Asian plates converge, causing the Eurasian plate to crumple up and the Indian plate to slide under, this caused the Himalayas and Tibetan mountains to be as high as they are. Transform boundary: A zone where two plates slide past each other (transform fault boundary), these are a major cause in the creation of Earthquakes such as the Oakland San Francisco Quake in 1989.

5.1.3. Mantle convection, ridge push, slab pull: 3 processes that cause the movement of the plates Mantle convection - Hot and less dense magma rises to the surface, dragging the plate along toward it. Ridge push - Magma that rises at mid-ocean level, cools and becomes more dense, gravitational forces make it slides away down the slope pushing the oceanic crust. Slab pull - Edge of a subducting plate is heavier and cooler than the mantel, as it goes deeper, it pulls the rest of the plate with it.

5.1.4. Canadian contributions to plate tectonic theory: Lawrence Morley, and British scientists Frederick Vine and Drummond Matthews, hypothesized that the magnetic striping along the ocean floor was caused by repeated reversals in Earth’s magnetic field. The discovery of magnetic striping indicated that the ocean floors were moving apart. Harold Williams helped to transform the notion of continental drift into the theory of plate tectonics, in the 1970s he described how mountain belts developed from colliding continents. Canadian geophysicist J. Tuzo Wilson was also pivotal in advancing the plate tectonics theory. His major contribution was that the Hawaiian islands formed over a stationary “hot spot” on the ocean floor, which eliminated the contradiction that volcanoes could be found several thousand km from the nearest plate boundary. Wilson also proposed that there must be a third type of boundary in which the plates slipped past one another which was the transform boundary

### 5.2. Seismic Waves

5.2.1. 4 TYPES OF WAVES P-wave, S-wave, Rayleigh wave, Love wave: P-Wave - fastest type of wave, they are compressional waves that push and pull and travel through rock and fluid, particles move in the same direction as the wave which is the same direction that the energy is moving in. S-Wave - moves slower than a P-wave and can only move through solid rock, S-waves move rock particles up and down, or side-to-side--perpendicular to the direction that the wave is traveling in. Rayleigh Wave - most dangerous, rolls along the ground just like a wave rolls across a lake or an ocean this rolling moves the ground up and down, and side-to-side in the same direction that the wave is moving. Love Waves - surface waves that are named after A.E.H. Love they are the fastest surface wave and they move the ground from side-to-side, Love waves produce entirely horizontal motion.

### 5.3. Earthquakes

5.3.1. Along Plate Boundaries: Most earthquakes occur along oceanic and continental plate edges. As the plates bump into and slide past each other, they stick because the surfaces of the plates are not smooth and the rocks catch on one another. The stress in the rock builds up until it breaks causing an earthquake, and after the earthquake, the plates continue to slide past one another until they stick again. Along Faults: Earthquakes also occur far from the plate edges along faults, which are cracks in the Earth where sections of the plate are moving in different directions. WHEN an earthquake occurs, the spot underground where the rock breaks is called the focus and it is the location of the earthquake. The location directly above on the surface is called the epicentre of the earthquake.

5.3.2. HOW EARTHQUAKES ARE MEASURED Richter and Mercalli scales: RICHTER SCALE - invented by Charles F. Richter in 1934, Richter magnitude is calculated from the amplitude of the largest seismic wave on the seismogram, this scale is a logarithmic scale, which means that each time you go up one unit on the scale, the motion recorded is 10 times greater. For example, an earthquake with magnitude 5 has 100 times more ground shaking than an earthquake with magnitude of 3. MERCALLI SCALE - Invented by Giuseppe Mercalli in 1902,uses the observations of people to estimate its intensity, this scale is not as scientific and relies on the reports of people who may over-exaggerate how bad the shaking was during the earthquake. Also, the amount of damage reported may not accurately record the strength of the earthquake because the amount of damage varies depending on: the building design; the distance to the epicentre; the type of surface material (rock or dirt) the buildings are on.

5.3.3. Seismograph, seismogram: Seismograph - An instrument used to measure and record Earthquakes, including force/duration. Seismogram - A record found using a seismograph. Used to find the time/length of a P-Wave, S-Wave and overall determine the radius/location that the Earthquake occurred at.

### 5.4. Journey to the Center of the Earth

5.4.1. Chemical and physical layers of Earth: Chemical Layers -The Crust: Outermost layer, continents and oceans are located here, variates in thickness from 35-70 km for the continents (mountains=thiccer) and 5-10 km in oceans, composed mainly of light rocks made out of silicon-oxygen and aluminium, less dense than mantle. -The Mantle: Layer under the crust, composed of rocks made out of silicon-oxygen, iron and magnesium, it’s 2900 km thicc and has two layers, the upper and lower Mantle. Internal heat of the Earth is located in the Mantle, and large convection cells drive the plate tectonic processes. -The Core: Two layers, outer liquid core composed of liquid nickel-iron alloy, is 2300 km thicc, while the inner liquid core is composed of only iron, is 1200 km thicc, liquid outer core creates the Eath’s magnetic fields. Physical Layers -The Lithosphere: Solid outer layer of the Earth, composed of the crust and solid portion of the upper mantle, it’s divided into plates that move due to tectonic forces. -The Asthenosphere: The “plastic layer” which the lithosphere floats on, part solid, part liquid. -The Mesosphere: Mostly solid, hot, and flows slowly. -The Outer Core: Is liquid, less pressure than inner core, high temp keeps rock in molten state. -The Inner Core: Is solid, higher pressure due to rest of the Earth surrounding it, temp could reach 9000°C.

5.4.2. Studies of Earth interior (seismology, sonar): Seismology - Seismic waves have played a major role in our understanding of the layers in the Earth, the waves travel at different speeds in different mediums therefore the type of material they travelled through can be inferred from seismic data recorded from major earthquakes at stations around the world. Sonar (Sound navigation and ranging) - Bouncing a sonar signal off of the ocean floor and measuring the length of time for the signal to return is how mapping of the ocean floor is accomplished. The length of time for the signal to return is used to calculate the distance (depth).

5.4.3. Liquefaction: A process in which the waves of an Earthquake amplify in softer-ground areas, causing the soil to loosen/”liquify” sending buildings and other structures into the ground.