Download Plate Tectonics and the Changing Earth NO PICS

(10) Solid Earth. The student knows that plate
tectonics is the global mechanism for major
geologic processes and that heat transfer,
governed by the principles of
thermodynamics, is the driving force. The
student is expected to:
(f) evaluate the role of plate tectonics with
respect to long-term global changes in Earth's
subsystems such as continental buildup,
glaciation, sea level fluctuations, mass
extinctions, and climate change.
Plate Tectonics’ Role in:
Continental buildup is simply the accretionary
process that helps continents to evolve. One
need only look to the Wilson Cycle to see how
continents evolve over time, from simple to
To the aged, and
complex.
dying
From the very, very
young
Without plate tectonics, the continents would only decline through weathering
and erosion.
Plate Tectonics’ Role in:
Tectonics dictate climate, and the key to glaciation is climate.
Glaciers atop mountains in temperate (lower) latitudes flow
downhill, scouring away the surface of the mountain. Over
millennia, such erosion can reduce the height and width of a
mountain range by miles.
However in very cold climates (and higher latitudes) such as the
Patagonian Andes, rather than scraping away the surface of the
mountain, glaciers protect the mountain top and sides from
erosion.
As glaciers move, they push about
great amounts of debris. When
continents are glaciated, they ride
Tectonics dictates latitude and
“lower” in the asthenosphere
altitude of places on Earth.
because of increased mass.
Plate Tectonics’ Role in:
At times during Earth's long history, the configuration of the
continents and seafloor have changed due to plate tectonics. This
affects global sea level by determining the depths of the ocean
basins.
The depth of the ocean
basins is a all about the age
of oceanic lithosphere: as
lithosphere becomes older,
it becomes denser and
sinks. The older the oceanic
lithosphere, the deeper the
ocean basin, the LOWER
the sea level.
The younger the oceanic
lithosphere, the shallower
the ocean basin, the
HIGHER the sea level.
The older basin is on the left side. On which
side would the sea level be higher?
Right!
The term "isostatic" refers to
The term "eustatic" refers to
global changes in sea level changes in the level of the
relative to a fixed point, such land relative to a fixed point in
as the center of the Earth,
the Earth, possibly due to
which results in an actual
thermal expansion or tectonic
change in the VOLUME of theeffects; it implies no change in
oceans. Eustatic sea-level
the
volume
of
water
in
the
changes occur when the
actual volume of the oceans oceans. As glaciers melt, the
continental mass decreases,
increases or decreases
perhaps through glaciation, orand the continent may
glacier melting.
“rebound”. No increase in
oceanic volume, but sea-level
to drop.
Much of sea-level rise today is“appears”
due to thermal
expansion. As sea
water warms, it expands.
When there were large amounts of continental crust near the
poles, the rock record shows unusually low sea levels during ice
ages, because there was lots of polar land mass upon which snow
and ice could accumulate.
Look at each of the following images of Earth in geologic past,
and determine if sea-levels would be low, or high…relatively.
Plate Tectonics’ Role in:
Movement of the continents into some configurations can cause or contribute to
extinctions in several ways.
• initiating or ending ice ages
• changing ocean and wind currents and thus altering climate
• opening seaways or land bridges which expose previously isolated
species to competition for which they are poorly adapted
Occasionally continental drift creates a super-continent which includes the vast
majority of Earth's land area, which in addition to the effects listed above is
likely to reduce the total area of continental shelf (the most species-rich part of
the ocean) and produce a vast, arid continental interior which may have
extreme seasonal variations.
It is widely thought that the creation of the super-continent Pangaea contributed
to the End-Permian mass extinction
Plate Tectonics’ Role in:
The distribution, elevation, and areal extent of the continents each
influence climate. In addition, plate tectonics influences climate by
modifying the atmospheric concentration of carbon dioxide.
Five major factors must be addressed:
• differences in surface albedo
Considering that the amount of incoming solar energy is very different at different latitudes, the latitudinal
distribution of land and sea has a strong potential to influence the total energy budget of Earth.
• land area at high latitudes
Land at high latitudes provides a surface for the accumulation of snow and year-round ice. Snow and ice have a
very high albedo; for fresh snow it approaches .65 to .80. Consequently, high-latitude land area, if snow-covered,
can also dramatically influence the Earth’s energy budget.
• transfer of latent heat
The largest energy fluxes at the surface of Earth involve moisture (latent heat flux). Clearly, the distribution of land
and sea will influence evaporation and precipitation and therefore the total energy budget of the atmosphere.
• restrictions on ocean currents
The distribution of land can block poleward heat transport by the ocean and may influence polar climates and the
subsequent extent of ice and snow cover. Thus, the shape and size of the ocean basins become a factor in
controlling global climate.
• thermal inertia of continents and oceans.
A continental surface has little thermal inertia. Basically, a continental surface responds rapidly to the current solar
input. In contrast, the oceans have a large heat capacity. Therefore, the thermal inertia of the oceans tends to
moderate the role of the seasonal cycle of insolation.