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3 | Earth Science in a Nutshell
Science in a Nutshell
(include destructive and constructive) - act on and transform Earth
materials. The processes are more important than the materials. All
processes and materials are interconnected and are brought together
through various cycles, described below.
What forces (energy sources, flow) drive these cyclic,
interactive processes and systems?
Plate Tectonic cycle - (See Fig. 1 below, click to zoom in)
is the ultimate recycling of the earth's materials through plate motions,
mantle convection, subduction, spreading ridges, volcanoes, earthquakes,
mountain building, etc. The source of energy to drive plate tectonics
is from latent heat of formation and radioactive decay. These release
energy, which is transferred by convection currents.
- Rock cycle - (See
Fig. 2, click to zoom in)
are three processes that form rocks: igneous, metamorphic, and sedimentary
processes. Any rock can become any type of other rock. The source of
energy for the rock cycle is both internal (convection currents, see
the plate tectonic cycle above) and external (the sun).
Igneous (Ig = fire): A
process of melting and cooling. Once on the surface, igneous rocks
weather, break down, and erode to form silt, sand, sediment, soil
etc. All of these can be "glued" back together into sedimentary rock.
Sedimentary rock can become igneous rock without going through a metamorphic
stage. Metamorphic rocks are baked and changed, but not melted.
Look back at the Plate
Tectonic cycle (Figure 1, above). Where would you find the formation
of igneous rocks? In mid-ocean
ridges and spreading centers, volcanoes and hot spots. Where would
you find the formation of sedimentary rocks? On the ocean
floor (carried by rivers) and on the surface of the earth. Where
would you find the processes to form metamorphic rocks? In subduction
zones and areas of mountain-building.
- Water Cycle - (See
Fig. 3, click to zoom in)
sun is the source of energy that drives this cycle. The products (shown
in Figure 3) are rain, fog, clouds, water, glaciers, snow, ocean, and
streams. The processes are condensation, precipitation, evaporation
The rock cycle and water cycle overlap with erosion, transporting,
Carbon Cycle - (See
Figs 4 and 5 below, click to zoom in)
is where the life cycle interacts with the rock cycle. Life decomposes
and releases carbon back into the soil, which eventually becomes sedimentary
rock. Burning fossil fuel also releases carbon (in the form of CO2)
into the atmosphere. There is a lot of CO2 trapped in rocks such as
limestones. Their weathering also releases CO2 into the atmosphere.
The short-term carbon cycle describes plant and animal respiration.
The long-term carbon cycle is determined by plate tectonics.