Earth and Space Science 

• the earth consists of the crust, mantle, outer core and inner core, all going deeper into the Earth in that order
• crust - consists of oceanic and continental crust
• oceanic crust - 6-10 km deep, average of 7, denser than continental crust, this causes it to subduct at collision areas 3 grams per cubic centimeter, younger/newer crust
• continental crust - thick, 10 - 70 km, with 35 km being the average, buoyant and less dense than oceanic crust, mostly old crust, 2.7 grams per cubic centimeter, made up of solid rocks and mineral, its temperature is like the atmosphere near the surface, but as you go deeper the temperature gets to around 200 - 400 degrees c
• mantle, middle layer of the earth, 2900 km thick, the deeper it is, the higher the temperature. varies from 1000 to 3000 degrees celsius depending on where it is, made up of solid rock - is solid, density is 4.5 grams per cubic centimeter
• outer core - the layer between the mantle and the inner core, 2200 km thick, made up of liquid iron and nickel constantly flowing, 4500 - 5500 degrees celcius, 12.6-13 g/cm3
• inner core - hot, dense ball of mostly iron at the centre of the earth, 1200 km radius, has such a large amount of pressure acting on it that it is solid, 5200 degrees celcius, 9.9 -12.2 g/cm3
• asthenosphere - part of the earth that is below the lithosphere, it is much hotter and much more fluid
• lithosphere - the solid part of the crust and upper part of the mantle, what tectonic plates are made up of
• the lithosphere and tectonic plates remain above the asthenosphere and float on it

practise questions relating to objective:

1. What does the Earth consist of ?
2. What is the density, temperature, and composition of each layer of the Earth?
3. What is the asthenosphere and lithosphere?

• there are multiple reasons as to why different layers have different compositions and densities, such as density and pressure
• the heaviest, most dense things sink deeper, while the lighter and less dense things rise, which causes the variation in composition
• additionally, the temperature of the layers changes as they are subjected to more and more pressure and go deeper into the earth
• the densities and pressures change because the layers deeper have pressure from the layers above pushing down on them, as well as gravity.

practise questions relating to objective:

1. Why does the temperature, pressure, and composition of each layer change?

• the theory of plate tectonics states that there are tectonic plates of the lithosphere floating on top of the asthenosphere, and moving due to mantle convection cells
• the earths crust is divided into 12 major plates
• the plates move, which causes them to either collide, pull apart, or scrape against one another
• each type of interaction causes a characteristic set of Earth structures or tectonic features
• tectonic - the deformation of the crust as a consequence of plate interaction

practise questions relating to objective:

1. Summarise the theory of plate tectonics.

• plates of the lithosphere are moved around by underlying mantle convection cells, areas where there are convection currents within the molten rock of the mantle

• plates of the lithosphere are moved around by underlying mantle convection cells, areas where there are convection currents within the molten rock of the mantle

  

hot material heated further deeper in the mantle moves upwards due to being less dense, while cooler material at the top of the mantle sinks downwards due to having a higher density. as a result, this forms a current. the once cool material heats up and moves upwards, while the hotter material cools down and sinks down again.

practise questions relating to objective:

1. What is the role of heat energy in plate tectonics?

• a fault - a fracture/break or series of breaks within the earths crust

  • can also occur at folds, where they break once the fold can no longer resist the strain
  • occur often along plate boundaries
  • occurs when stress is applied too quickly or stress is too great

• stress - a force that acts on a material

• strain - the change that the material undergoes under the stress

• foot wall - a slope you would put your feet on

• hanging wall - a slope that you would hang from

• there are different types of faults, that are determined depending on the type of stress applied to it

• stress types:

  • compressional - push
  • tensional - pull
  • shear - slide past each other

• types of faults:

  • normal fault - caused by tension
  • reverse fault - caused by compression
  • transform fault - caused by shear stress

• the type of fault not only relies on stress, but how the hanging and foot walls move relative to each other

• normal fault - occurs at divergent plate boundaries, occurs under tensional stress

• reverse fault

• occurs at convergent boundaries

• occurs under compressional stress

• transform fault / strike slip fault

• occurs at transform plate boundaries

• occurs under shear stress

• folds occur under compressional stress, when stress is applied to both ends of a section of a rock or rock layers

• some rocks might break, but a fold occurs when the rocks bend

• anticline - fold in the shape of an ‘n’

• syncline - fold in the shape of a ‘u’

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practise questions relating to objective:

1. What is a fault?
2. What are the different types of faults?
3. What is a fold? Under what conditions does it occur?
4. Define anticline, syncline, compressional stress, tensional stress, and sheer stress
5. What are the hanging and foot walls?

• seafloor spreading occurs commonly at mid-ocean ridges, when two plates move away from each other (divergent plate boundary) causing volcanic activity in which new rock is formed from magma flowing out from the ridge

  

practise questions relating to objective:

1. What is seafloor spreading?
2. What causes seafloor spreading?

• volcanism and earthquakes are mainly focused at plate boundaries as that is where most tectonic activities occur

• volcanoes can be formed in multiple ways:

  1. subduction - subducting slab will melt into magma once it is pushed deep enough, and then be erupted once again at the surface
  2. rifting - when two plates move apart magma rises (sea floor spreading) and causes volcanic eruptions at the surface
  3. at hotspots, which do not occur at tectonic plate boundaries but appear anyway. a hot mantle plume breaches the crust in the middle of a tectonic plate. a chain of volcanoes may be formed as the tectonic plate moves above the hotspot

• earthquakes also mainly occur at plate boundaries

• this is because of applied stress, the plates may push against each other (for example, transform plate boundaries)

• this causes earthquakes as the energy is released from the stress, and even more so it the plates were under tension/pressure for a long time

• constructive plate boundaries - divergent plate boundaries

• destructive plate boundaries - convergent plate boundaries

practise questions relating to objective:

1. How are volcanoes formed?
2. What causes earthquakes?
3. What are constructive/destructive plate boundaries?

• convergent plate boundaries - two plates are pushing together
• divergent plate boundaries - plates are pulling apart
• transform plate boundaries - plates slide against each other

practise questions relating to objective:

1. What are the different types of plate boundaries?

   

Essentially, where there are all of the plate boundaries, there are volcanoes and earthquakes because that is where tectonic processes occur.

practise questions relating to objective:

1. Where do earthquakes and volcanoes occur?

• there are large amounts of evidence to support the theory of plate tectonics, such as:
  • fossils - fossils of the same species are found on different continents. as they animals couldn’t have moved, it means that the continents were together at some point
  • continental shores - the shores of the continents all fit together as if they are a puzzle, further proving that they continents were together at some point
  • hot spot volcanoes - the movement of plate tectonics over hotspots can be seen in the shape of the mountain and volcano ranges

practise questions relating to objective:

1. What evidence supports the theory of plate tectonics?

• Australia has a lot of volcanoes, but none of them have erupted for the past 5000 years
• this is because Australia is located in the middle of a tectonic plate, and is far away from any plate boundaries

practise questions relating to objective:

1. Why is the Australian continent so stable?

• seismographs - detect seismic/shock waves underneath the ground and can predict when an earthquake is approaching
• creepmeter - measures the movement of fault lines to determine if slow movement is taking place, which could potentially lead to earthquakes
• Randon gas and other fumes are measured within the atmosphere and if detected in large amounts, it could suggest an earthquake approaching
• creating artificial seismic waves and measuring their impact as well as behaviour of the crust can help determine its contents
• gps positioning - measure the distance travelled by a station or location that can help determine the size of the earthquake

practise questions relating to objective:

1. What is some technology used to predict earthquakes in asia-pacific regions?

• rock - any solid mass that is naturally occurring or aggregate of minerals or mineraloid matter
• mineral - a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in a pure form
• ore - a natural rock or sediment that contains one or more valuable minerals
• crystal - a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions
• igneous rocks
  • formed when magma or lava cools down and solidifies into rock
  • can be formed both underground and above ground
  • if above ground - volcanic/extrusive, and has smaller crystals
  • if underground - plutonic/intrusive, and has large crystals
• sedimentary rocks
  • rocks formed by the compaction and sedimentation of sediments
  • formed on or near the earth’s surface, unlike metamorphic or igneous rocks
• metamorphic rocks
  • formed when intense heat and or pressure modifies already existing rock, changing igneous, sedimentary and other metamorphic rocks
  • minerals can become foliated, or squashed into long strips
  • chemical compounds may change
  • formed very deep underground under areas of lots of pressure

practise questions relating to objective:

1. What are the 3 types of rocks? What characterises each one?
2. Define the terms rock, mineral, ore and crystal.

• igneous rocks are formed as magma solidifies - therefore, they are solidified moletn material
• can be plutonic or volcanic:
  • volcanic / extrusive - formed above ground
  • plutonic / intrusive - formed under ground
• volcanic rocks have smaller crystals within them as they have less time to form as the magma cools down
• however plutonic rocks often have large crystals as they cool down slowly, meaning the crystals have more time to form

practise questions relating to objective:

1. What are igneous rocks?
2. What are the two types of igneous rocks? How can you tell them apart?

• metamorphic rocks form after being subjected to large amounts of pressure and intense heat
• recrystallisation - a metamorphic process that involves the altering of a rock on an atomic level, where the crystal structure changes

practise questions relating to objective:

1. What are metamorphic rocks?
2. What is recrystallisation?

• sedimentary rocks are formed via the processes of weathering and erosion
• weathering: the break down of rocks into smaller materials
  • physical weathering - weathering during which the chemical composition of the rocks isn’t altered
  • biological weathering - weathering influenced or caused by natural processes such as plants, animals, bacteria or fungi
  • chemical weathering - the chemical composition is altered as the rock is broken down
• erosion - the natural processes such as water or wind that remove soil, rock, or dissolved material from one location on the Earth’s crust and then transports it to another location where it is deposited
• often, the sediments are carried to water bodies where they accumulate
• after a while, or several layers, the pressure along with the crystallisation of chemicals in the water creates layers of cemented rock
• this is how sedimentary rock is formed
• there are 3 types of sedimentary rock :
  • clastic - form from naturally weathered sediments, and bound by natural cements (for example, calcite, silica, gypsum
  • chemical - formed when dissolved chemicals within water crystallise and form rock
  • organic - formed from dead animal or plant matter

practise questions relating to objective:

1. What is weathering?
2. What is erosion?
3. What are the 3 types of weathering?
4. what are the 3 types of sedimentary rock?
5. How are sedimentary rocks formed?

• metamorphic rocks
  • often have layer structures of crystals due to pressure
  • tend to be harder and denser
  • layers of crystals can often have distortions shown via zig zag patterns due to movement occurring while they form
  • two types of metamorphic rocks:
  • regional metamorphism - occurs over a wide area, often due to tectonic plate boundaries
  • contact metamorphism - occurs in localised areas, often around plutonic igneous rocks
  • burial - pressure formed by many layers of rock pushing down causing the rock to recrystallise
  • shock - occurs under sudden force, pressure or heat, such as with a meteorite strike
  • seafloor - occurs due to high temperatures at mid-ocean ridges
  • examples of metamorphic rocks (increasing heat and pressure) - shale, slate, phyllite, schist, gneiss
• igneous rocks
  • never have fossils in them
  • the rock depends on the magma that forms it, as it can have different contents and viscosities
  • made up of interlocking crystals
  • granite, basalt and obsidian are examples of igneous rocks
  • typically hard and strong
• sedimentary rocks
  • 3 types (mentioned before) - each one has different properties
  • clastic
  • horizontal layers, often visible
  • grains/clasts do not interlock, you can see cement between them
  • can contain fossils
  • chemical
  • often quite soft
  • has visible crystals
  • very rare fossils and layering
  • organic
  • usually soft, sometimes layered

practise questions relating to objective:

1. What are the properties of sedimentary, metamorphic and igneous rocks?
2. what are the 5 types of metamorphism?
3. what are the 3 types of sedimentary rocks?

practise questions relating to objective:

1. Draw the rock cycle

• limestone, sandstone and shale - sedimentary
• granite - igneous
• limestone → marble
• sandstone → quartzite
• shale → slate
• granite → gneiss

practise questions relating to objective:

1. What type of rocks are limestone, sandstone, granite and shale?
2. What do they metamorphose into?

• limestone, sandstone and shale - sedimentary
• granite - igneous
• limestone → marble
• sandstone → quartzite
• shale → slate
• granite → gneiss

practise questions relating to objective:

1. What type of rocks are limestone, sandstone, granite and shale?
2. What do they metamorphose into?

• largest unit of time is an eon
  • eons
  • eras
    • periods
    • epochs
• scientists use the terms late, middle and upper to define the amount of time and part of a period or other unit of time
• upper - usually more millions of years while late is usually less
• eon - several hundred million of years
  • era - tens to hundreds of million of years
  • period - millions of years to tens of millions years
  • epoch - millions of years to thousands of years
• major geological events using a timescales:
  • earth formed 4700 million of years ago
  • oldest rocks were formed 4300 million of years ago
  • oldest life was formed 3800 million of years ago
  • the first vertebrates appeared 500 million years ago
  • first mammals appeared 200 million years ago
  • first primates appeared 65 million years ago
  • first homo sapiens appeared 2 million years ago

practise questions relating to objective:

1. how long is an eon, era, period and epoch?
2. what are the terms upper, middle and late mean?
3. when was earth formed, oldest rocks formed, oldest life formed, first vertebrates appearing, first mammals appeared, first primates appeared, first homo sapiens appeared?

• a solid, naturally occurring inorganic substance
• in order for something to be a mineral, it has to be:
  • be naturally occuring
  • solid under normal conditions
  • be inorganic
  • have a fixed chemical composition
  • have a specific atomic arrangement

• a solid, naturally occurring inorganic substance
• in order for something to be a mineral, it has to be:
  • be naturally occuring
  • solid under normal conditions
  • be inorganic
  • have a fixed chemical composition
  • have a specific atomic arrangement

practise questions relating to objective:

1. Define mineral

• a solid, naturally occurring inorganic substance
• in order for something to be a mineral, it has to be:
  • be naturally occuring
  • solid under normal conditions
  • be inorganic
  • have a fixed chemical composition
  • have a specific atomic arrangement

practise questions relating to objective:

1. Define mineral