The Lithosphere
Form a group of 4
Responsibilities for group member:
1.
2.
3.
4.
This person keeps groups on task.
Responsible for drawing up the cycle.
Takes care of writing up the question and answers for the focus questions.
The final person organises information for group presentation.
Tasks:
a.
b.
c.
d.
Read the 4 readings, one each.
(10 minutes)
Answer the focus questions collaboratively.
(30minutes)
Complete the diagram of the water cycle.
(20 minutes)
Organize information and prepare a short presentation to class. Presentation should
include your cycle, and human impacts affecting the cycle.
(30minutes)
Focus questions:

What is the Lithosphere, and what are three rock types that make up the
lithosphere?

What are the layers in the Lithosphere? Illustrate with a cross section diagram.

What are tectonic plates?

How have humans affected the lithosphere?
Crust, the upper layer of the Earth, is not always the same. Crust under the oceans is only
about 5 km thick while continental crust can be up to 65 km thick. Also, ocean crust is made
of denser minerals than continental crust.
The tectonic plates are made up of Earth’s crust and the upper part of the mantle layer
underneath. Together the crust and upper mantle are called the lithosphere and they
extend about 80 km deep. The lithosphere is broken into giant plates that fit around the
globe like puzzle pieces. These puzzle pieces move a little bit each year as they slide on top
of a somewhat fluid part of the mantle called the asthenosphere. All this moving rock can
cause earthquakes (http://www.windows2universe.org/earth/interior/earths_crust.html)
The lithosphere is the brittle outer layer of the solid Earth. The plates of plate tectonics are
segments of the lithosphere.
The lithosphere is basically the layer of the Earth that is strong enough to flex rather than
flow. Its top is easy to see it's at the Earth's surface but the base of the lithosphere is a
transition rather than a sharp boundary. The details of that transition are an active area of
research.
The lithosphere is not totally rigid, but slightly elastic. It flexes when loads are placed on it or
removed from it. Ice-age glaciers are one type of load. In Antarctica, the thick ice cap has
pushed the lithosphere well below sea level today, for example. In Canada and Scandinavia,
the lithosphere is still unflexing where the glaciers melted about 10,000 years ago.
The flexing of the lithosphere from these causes is relatively small (usually much less than a
kilometre), but measurable. We can model the lithosphere using simple engineering physics,
as if it were a metal beam, and get an idea of its thickness. (This was first done in the early
1900s.) We can also study the behaviour of seismic waves and place the base of the
lithosphere at depths where these waves begin to slow down, indicating softer rock.
These models suggest that the lithosphere ranges from less than 20 kilometres in thickness
near the mid-ocean ridges to about 50 km in old oceanic regions. Under the continents the
lithosphere is thicker, from around 100 to as much as 350 km.
These same studies show that underneath the lithosphere is a hotter, softer layer of solid
rock named the asthenosphere. The rock of the asthenosphere is viscous rather than rigid
and deforms slowly under stress, like putty. Therefore the lithosphere can move across or
through the asthenosphere under the forces of plate tectonics. This also means that
earthquake faults are cracks that extend through the lithosphere, but not beyond it.
The Sierra Nevada Mountains, California
BACKGROUND:
Igneous rocks come in many varieties. However, all igneous rocks began as molten rock
(magma) which cooled and crystallized into minerals. Igneous rocks may look different
because of two factors: (1) they may have cooled at different rates and (2) the "mother"
magma (original melted rock) was of a different composition. Variations in these two factors
have created many different types of igneous rocks. When the magma cools at different
rates, it creates different sized minerals. Quick cooling magmas have small minerals (with
the exception of obsidian, which is actually composed of silica, but has no crystalline
structure). Basalt, for example, has small minerals, most of which can only be seen under a
microscope. Magma that cools slowly creates rocks like granite which have large minerals
that can be seen with the naked eye. Geologists classify igneous rocks based on both their
crystal size and composition. The Rock Cycle has its origin in Igneous Rocks.
Sedimentary rocks form at the Earth’s surface in two main ways: (1) from clastic material
(pieces of other rocks or fragments of skeletons) which have become cemented together,
and (2) by chemical mechanisms including precipitation and evaporation. Sedimentary rocks
are usually associated with liquid water (which facilitates erosion, transportation,
deposition, and cementation). However, sedimentary rocks may also form in dry, desert
environments or in association with glaciers.
Metamorphic rocks are igneous, sedimentary, or pre-existing metamorphic rocks that have
been changed by great pressures and temperatures within the crust and upper mantle of
the Earth. The temperatures were not enough to melt the rock; otherwise, an igneous rock
would have formed. The pressures were much greater than those required to simply break
the rocks into pieces. They were high enough to change the chemical make up of the rock by
forcing the elements in it to "exchange partners."
All three types of rock make up the Earth’s lithosphere, the outermost layer. The
lithosphere averages about 100 kilometres in thickness. It is like an eggshell compared to
the Earth’s total radius (the distance from the Earth’s core to the surface). The lithosphere is
solid rock. Sedimentary rocks are the most abundant rock only on the surface of the Earth,
but igneous and metamorphic are abundant deeper into the mantle.
IGNEOUS ROCK = hot rocks or melted rocks (ask students to think of hot areas) are found:

volcanoes

inside the Earth (not near the centre, more toward the outside, within the
crust)
SEDIMENTARY ROCKS = cool, wet, or fossil rocks (ask students to think of water) are found:

rivers

oceans

lakes
METAMORPHIC ROCK = changed, squished, or "rhinestone" rocks (ask students to think of
squishing) are found:

inside the Earth (not near the centre, within the lithosphere and upper
mantle)
Human impact on the Lithosphere
How do fertilizers impact the soil?
Fertilizers add nutrients to soil which can make it difficult for microorganisms to produce
nutrients naturally and add to water pollution.
How does farming lead to soil loss?
When land is cleared for farming trees are cut down and vegetation is removed leading to
soil loss.
How does overgrazing of land cause?
Overgrazing causes vegetation to be removed, soil loss, and desertification of the land.
What are three activities that lead to soil loss?
Construction, development, and mining.
What are three negative impacts from soil loss?
Soil loss causes pollution on land, pollution in water, and loss of fertile soil for growing
crops.
What are four farming methods that farmers can use to reduce soil loss?
No-till farming, contour plowing, terracing, and use of wind breaks.
Which farming method involves building platforms along a hill to reduce soil loss?
Terracing
Which farming method involves not tilling the land between growing seasons to reduce
soil loss?
No-till farming
Which farming method involves plowing along the contours of a hill to reduce soil loss?
Contour plowing
Which farming method involves planting rows of trees along fields to reduce wind erosion
of fertile soil?
Wind breaks
Which farming method involves rotating types of crops grown from one season to the
next to conserve soil fertility?
Crop rotation
What is one step that land developers can take to reduce soil loss?
Reduce the amount of removal of trees and other vegetation during land development.
How has remote sensing such as the use of satellite imaging helped to reduce soil loss?
Remote sensing can tell us how humans are constantly changing the Earth's surface and the
impact it is causing in order to find solutions and prevent soil loss.
Why is it important for humans to be good stewards of the pedosphere?
Good, fertile soil is an important resource we need to feed a growing population and
humans should always monitor and try to reduce pollution of land and water for future
generations.
Source: http://quizlet.com/29023112/human-impact-on-the-lithosphere-flash-cards/