lesson 1 overview + geosphere + earth structure, geologic time and plate tectonics Flashcards
Mechanism of earth?
The interactions between the six sphere: geosphere, atmosphere, hydrosphere, celestial sphere, biosphere and anthroposphere explains the impacts and processes that occurs on earth
The principle of uniformitarianism definition?
The assumption that the same natural laws and processes tha toperate in the universe now have always operated in the universe in the past, and thus apply everywhere
What are compositional layers?
Compostion is based on the elements present. Oceanic crust is thinner and thus surfaces are of lower altitude, allowing water to pool and form oceans. Continental crust it hicker, above sea level and less dense.
More dense, thinner / lower altitue –> Oceanic
Less dense, thicker –> Continental
What is oceanic crust primarily made out of ?
Basalt (3.0g/cm^3)
What is continental crust primarly made out of?
Granite (2.7g/cm^3)
Define mechanical layers
Based on the physical states of the layers
–> solid lithosphere, extremely viscous fluid aesthenosphere, convecting solid mesosphere, liquid outer core, liquid outer core, solid inner coure
What are the four layers of compositional layers?
Continental crust, oceanic rust, mantle and core
What are the five layers of mechanical layers?
Lithosphere, aesthenosphere, mesosphere, outer and inner core
What are the three most common minerals found in Earth’s crust?
Oxygen (49%), Silicon (26%) and aluminium (7%)
What are most rocks composed by?
Si and O are the most abundant, and most minerals in the crust are composed of silicates (anionic compound of Si and O)
Silicate minerals are the most common of Earth’s minerals and include quartz, feldspar, mica, amphibole, pyroxene, and olivine. =
What is another common compound other than silicates?
due to abundance of oxygen, oxides can be found
Radioactive isotopes
Some isotopes of elements are radioactive and can decay into daughter elements.
- -> the ratio of daughter element with the radioactive isotope present can provide us information about how much time has elapsed since th emineral was last heated / formed.
- -> known as radiometric dating
What is the geologic time scale?
A timeline of Earth’s history based around life.
Each period are determined by first and last appearance of certain index fossils.
Simplified goelogic time scale includes eras:
From oldest to youngest: Hadean, Archean, Proterozic, Paleaoxoic, Mesozoic, Caenozoic
Plate tectonics
The lithosphere consists of brittle, rigid “plates” that move on top of the aesthenosphere at very slow speeds. This has consequences ofr the transfer of energy, types of rocks formed, evolution of climate in locations and local biology.
What is the most important determination when identifying rocks?
Tectonic setting in which they were formed (stratas, environment, changes, uncomformities etc….)
What are the three evidence sfor plate tectonics?
- > some fossils are found across continents across oceans
- -> continent edges, when mapped at the continental shelf, fits like jigsaw puzzles
- -> plate fault boundaries evidence is visible (divergent mid-ocean ridges_
What are the movement mechanism for plate tectonic movements?
- > plates are rigid - so forces on one component will be transferred across the rest of the plate
- > magma convection currents caused by core rise at divergent areas creating a ridge push
- > density difference of cold, dense subducting plate with hot light aesthenosphere creates “slab pull” from gravity
three types of plate boundaries?
convergent -> plates moving towards each other
divergent boundaries -> plate smoving away from each other
transform -> plates moving past each other
Some significant features at convergent boundaries?
- continental continental : mountains due to density similarity, also creates large earthquakes due to
- oceanic continental : oceanic trench –> leading to island arc, or volcanic arcs
- oceanic oceanic : volcanoes, causing earthquakes
What forms at divergent boundaries?
- oceanic oceanic: mid ocean ridge, producing new oceanic crusts from magma, volcanic activity in fissure eruptions, shallow earthquake activity,
- oceaninc and continental: potentially form rift valleys
- continental continental: form rift valleys, that then forms a ridge and is called mid ocean ridge, forming more newer oceanic crusts
