Part III: The Earth - Atmosphere Interface This includes section 3_1 to 3_5. I have typed out everything that Quinton has said and even added a little extra for explanation. It includes practice quiz questions at bottom. If something is highlighted, than
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Part III: The Earth - Atmosphere Interface
3_1 The Dynamic Planet – Chapter 11
The Geological Cycle
While the endogenic (internal) system is at work building landforms, the exogenic (external) system is
wearing them down. The vast give-take at the Earth-atmosphere-ocean interface is the geological cycle.
It is fuelled by internal heat and solar energy from space and is influenced by the ever present levelling
force of Earth’s gravity.
The hydrological cycle is the vast system that circulates water, water vapour, ice, and energy
throughout the environment. It rearranges Earths materials through erosion, transportation, and
deposition, and it circulates water.
The rock cycle: through the processes in the atmosphere, crust and mantle, 3 basic rock types are
produced – igneous, sedimentary and metamorphic.
The tectonic cycle: brings heat energy and new materials to the surface and recycles old materials to
mantle depths, creating movement and deformation of the crust.
Mantle consists of 80% of earth’s volume. Become less and less dense as you come closer to the surface.
Also becomes hotter and stiffens the deeper you go because of pressure. Upper mantle is broken up
into three parts; upper mantle, asthenosphere, and uppermost mantle. Uppermost mantle consists of
Earth is structured in layers. Below methosphere, is upper/lower mantle, outer/ inner core. Our
discussion is mainly on the lithosphere.
Lithosphere - Crust(continental(c.c. made of granite 2700 kg/m3)(crystalline) or oceanic(o.c. made of
Basalt 3000kg/m3)(granular) then uppermost mantle (umm). Lithosphere is rigid rock.
Asthenosphere (plastic layer) – can move both ways depending on load or weight on it. Can react to
weight. The oceanic crust above it is thinner than the continental crust above it. The thick c.c. pushes
lithosphere downward (more than o.c.)
Isostacy – Iso (means equal) the mechanism whereby areas of the crust rise or subside, until their mass
is supported or compensated by the asthenosphere below. The asthenosphere can do that because it
Plate tectonics - The theory describing the motions of continents and ocean basins and the processes
that fracture and fuse them. Plates move at the same rate that fingernails grow.
Earthquake is a resistance to movement which causes a sudden jerk.
Convection causes plates to move. From a heat gradient caused from the core. Divergence when plates
move away from each other. This causes convergence further down (plates move below or above
6 Major Plates – Pacific plate, Nazca plate, South American plate, African plate, Indo-Australian plate,
Eurasian plate. The minor plates are called platelets.
There are always plates present even during divergence. During divergence, material moves to fill the
Dynamic Equilibrium – tells us that the rate of production of new plates is equal to the rate of
destruction of the plates.
Processes on earth run by energy given by the sun.
Lithospheric crust circles the entire globe. They move around.
If separation of plates is slow than there is vertical build up called mid-ocean ridge. If fast than there is
not enough time to vertically build. Only called mid-ocean ridge if located in ocean.
Plates separate and fills up with water. Eventually it builds up a new ocean. Mid-ocean ridge is created.
But spreading may stop if too much resistance so not necessarily becoming an ocean every time.
Spreading Boundaries – Ocean ridges occur because of rise of magma to form a mountain range.
Plate tectonics explains:
- Shape of ocean basins
- Relatively young age of oceanic crust
- Age distribution of oceanic crust (oceanic crust constantly recycled) (The crust closer to the oceanic
ridge is youngest and gets older going out)
- Transform faults
- Geomagnetic patterns – Most magnetic at the oceanic ridge.
- Fit of the continents
- Similarities between distant continents
- Characteristic of sea-floor spreading centres
- Upwelling material from the mantle forms new seafloor and lithospheric plates spread apart
- Mostly occurs at mid-ocean ridges but a few within continents themselves
- Continental – oceanic
- Oceanic – oceanic (when 2 oceanic crusts are in contact)
- Continental – continental
- Melting of plate is equal to creation of new plate boundary.
- Sediment wedge is developed from sediment being scraped off of crust while it is submerging
- Volcanic chains are created on top of area that crust is melting because magma rises (hot spots).
- When continental crusts are moving to each other and there is ocean crust between them, the
ocean is drained. The oceanic crust is moved upwards and creates a mountain range. This mountain
range is created by collision, not volcanic creation.
- Orogeny – period of intense tectonic activity
- Orogen – mass of strongly deformed rock including igneous rocks produced during an orogeny
- Suture zone – Long band of intense tectonic deformation formed during a continental collision
- Terrane – Section of continental crust distinct from adjacent continental crust
- Plates slide laterally past one another at right angles to a sea-floor spreading centre
- Neither diverging nor converging and usually with no volcanic eruption
Plate tectonics explains:
- Location of volcanoes
- Distribution of earthquakes (earthquakes greatest near plate boundaries)
- Location of mountain ranges (during subduction and collision of c.c. with ocean crust between)
- Orogens - Orogeny refers to forces and events leading to a severe structural deformation of the
Earth's crust due to the engagement of tectonic plates.
- Terranes - a fragment of crustal material formed on, or broken off from, one tectonic plate and
accreted or "sutured" to crust lying on another plate.
- Location of oceanic trenches
Tectonic Settings and volcanic Activity
- Some cases magma is acidic which is less viscous (flows more easily) and causes spreading out of
material instead of creating mountains.
- Hot spots melt oceanic crust and magma rises and creates mountains and volcanoes. This is how
Hawaii was created.
- A long wave is formed when oceanic crusts converge which causes an earthquake. Barely notice
until it reaches land and builds vertically.
Transform boundary in west coast
Hot spot – hot spot at top of asthenosphere. The layer going over it will experience heating. Hot spot
creates a line of hot spot volcanoes. Line doesn’t have to be straight because plate above can change
direction. Older hot spot volcanoes are usually below sea level caused by erosion from waves.
Hawaii has a hot spot volcano. Its hot spot created volcanoes before it around 38 million years ago.
Hawaii is in the middle of a plate but still has lots of plate activity.
Volcanoes are along the coasts because of subduction.
While the endogenic (internal) system is at work building landforms, the exogenic (external) system is wearing them down. The vast give-take at the earth-atmosphere-ocean interface is the geological cycle. It is fuelled by internal heat and solar energy from space and is influenced by the ever present levelling force of earth"s gravity. The hydrological cycle is the vast system that circulates water, water vapour, ice, and energy throughout the environment. It rearranges earths materials through erosion, transportation, and deposition, and it circulates water. The rock cycle: through the processes in the atmosphere, crust and mantle, 3 basic rock types are produced igneous, sedimentary and metamorphic. The tectonic cycle: brings heat energy and new materials to the surface and recycles old materials to mantle depths, creating movement and deformation of the crust. Become less and less dense as you come closer to the surface. Also becomes hotter and stiffens the deeper you go because of pressure.