Transcript Erosion and Deposition Notes Part 2 File

(11) Solid Earth. The student knows that the geosphere
continuously changes over a range of time scales involving
dynamic and complex interactions among Earth's
subsystems. The student is expected to:
(b) explain how plate tectonics accounts for geologic surface processes and
features, including folds, faults, sedimentary basin formation, mountain
building, and continental accretion;
•Students understand how tectonics affect topography
(c) analyze changes in continental plate configurations such as Pangaea and
their impact on the biosphere, atmosphere, and hydrosphere through time;
(d) interpret Earth surface features using a variety of methods such as
satellite imagery, aerial photography, and topographic and geologic maps
using appropriate technologies
Vocabulary: Orogeny
As you have already learned, tectonic processes originate within the planet and
produce movements of the Earth's crust.
There are basically two types of pressures exerted on the crust:
• Compression
has a tendency to shorten the Earth's surface ,resulting in the wrinkling of the
crust. What type of plate boundary may this process occur at?
• Tension
causes the crust to crack or fracture, while pulling it apart. Tension tends to
stretch or expand the surface. What type of plate boundary may this process
occur at?
Folding refers to the wrinkling of the crust which occurs because of slow lateral
compression. When layered flat strata are subjected to compressional forces, they are
bent and deformed. Too much bending creates a break, or a fault.
By far, most of the Earth-forces are compressional.
Fold patterns may be simple or very complex in form, due to the varying intensity of the
tectonic forces that produced them. Either way, they leave clues behind for geologists to
interpret and discover their origins.
What are the two types of forces at work on the planet’s surface?
What types of plate boundaries do you associate with
compression forces?
What types of plate boundaries do you associate with tension
forces?
Compression forces cause f__________ of sediment, and
f__________ appear when too much of this occurs.
Various shapes and forms of folding are the following:
Monocline:
The simplest type of fold. It involves only one inclination of the rocks. In a monocline the
fold is bent in one direction only.
Anticline:
When the pressure exerted on a rock is not great, a series of simple folds are produced.
In such folds the arches or up-folds, or crests, are called anticlines.
Syncline:
In a simple fold, the troughs or down-folds are called synclines. The sides of the folds
between the anticlinal crests and synclinal troughs are called the fold limbs.
Recumbent Fold:
A fold in which the limbs (waves) are largely horizontal. Geologically speaking, it is
inferred that these folds were at one time vertical, and through extreme geologic
upheaval, have been “upended”.
When rock strata are strained beyond their ability to fold, and retain their solid state as a
unit, they fracture, or break. When a fracture occurs and the rocks are displaced on
either side of it relative to one another, the result is known as a fault, and the process is
faulting.
•Faults often occur in groups
along a fault zone. Some faults
displace rocks up and down. This
is called vertical displacement.
•Some faults cause lateral
displacement or sideways
movements.
When there are sudden slippage
movements, it generates
earthquakes.
A single fault movement may result in slippage ranging from a centimeter to about 15
meters. Such slippage may occur in quick succession or may occur after gaps of several
decades or centuries. The cumulative displacement may involve as much as hundreds
of kilometers.
Type of fold represented
in this photo:
The crests of this fold are
known as:
The troughs in this fold
are known as:
The simplest fold is
known as a:
The tension fault or normal fault:
A normal fault occurs where tension causes fracture in rocks that are being pulled apart.
The rock above the fault plane moves down relative to the rock beneath the fault plane.
The reverse fault or thrust fault:
Reverse fault occurs where compressional force causes the upper block of rock to be
pushed over the lower. As a result of compressional forces there is shortening of the
crust.
The strike-slip fault:
A strike-slip fault is a fault on which the two blocks slide past one another. These faults
are identified as either right-lateral or left lateral depending on whether the displacement
of the far block is to the right or the left when viewed from either side. The San Andreas
Fault in California is an example of a right lateral fault.
A _________ fault, or normal fault is caused by tension forces,
pulling the pieces apart.
A ________ fault, is the result of compression forces, pushing the
pieces together.
The _____________ fault is the result of lateral movement.
Strike-slip faults form along ____________ plate boundaries.
SEDIMENTARY BASIN FORMATION
Sedimentary basins are created by depressions (dips) in the surface of the lithosphere
associated with tectonic processes. These topographic and bathymetric (beneath the
water) basins are subsequently filled by sediment, leading to further subsidence and
sediment accumulation.
Sedimentary basins are
important, because
petroleum is most often
found in such locations.
A sedimentary basin is
a depressed area of
the Earth’s crust where
tiny plants and animals
lived or were deposited
with mud and silt from
streams and rivers.
These sediments eventually hardened to form sedimentary rock. The soft parts of plants
and animals, exposed to heat and pressure over millions of years, gradually changed to
oil and natural gas. Coal is formed from the remains of ancient fern-like trees that died in
swamps, and were compressed over the millennia. Temperature, pressure and
compaction of sediments increase at greater depths.
MOUNTAIN BUILDING: OROGENY
The terms orogeny and orogenesis involve tectonic processes that result in the
formation of mountain chains. Mountain building most commonly involves the collision
between two continental lithospheric plates. Because continental plates are of relatively
equal density, when they converge, they crinkle up. These are known as “folded
mountains”. When the plates carrying Africa and Saudi Arabia, along with other smaller
plates, collided (from the south) with Eurasia in the north, the Alps formed.
When these boundaries
form subduction zones,
most often, volcanic
mountains arise, such as
the Andean orogenics. It
results from the
subduction of the oceanic
Nazca plate underneath
the South American
continent. Collision
follows subduction of
oceanic lithosphere
beneath one continent.
Topographic features are found ___________
___________ means the “origin” of mountains.
Bathymetric features are found____________
Describe the two different types of mountains, and what types of
plate boundaries they may form along. Give examples of each.
Sedimentary basins are especially important because this is
where ________________ form.
CONTINENTAL ACCRETION
Accretion is a process by which material
is added to a tectonic plate or a
landmass. There are two possible ways
Amazon Alluvial Deposit
this may happen.
•Tectonic Accretion:
 Volcanic island arcs or seamounts may collide
with the continent, and as they are of relatively
light material, they will often not be subducted, but
are thrust into the side of the continent, thereby
adding to it.
•Landmass Accretion:
This involves the addition of sediment to a
coastline or riverbank, increasing land area via
erosion and deposition. The most noteworthy
landmass accretion is the deposition of alluvium,
often containing precious metals, on riverbanks
and in river deltas.
Give an example of tectonic accretion.
Give an example of landmass accretion.
SUPERCONTINENTS
Pannotia; a time of
great glaciation
Formation of supercontinents, such as
Rodinia, greatly influences climate. Climate
influences life.
Since Rodinia formed during a time when
life consisted only of bacterial forms, such as
stromatolites, it must have been a vast and
desolate place. Life had not yet colonized
land.
The eight continents which made up Rodinia
later reassembled briefly into another super
continent Pannotia, and again into Pangaea.
Rodinia produced some significant changes in
the Earth. It was the largest landmass to have
existed up till that time. It significantly
changed ocean currents, which may have led
to snowball Earth later in the Cryogenian.
ENVIRONMENTS
The formation of a supercontinent can dramatically affect the environment. The collision
of plates will result in mountain building, thereby shifting weather patterns. Sea levels
may fall because of increased glaciation in mountains and continental interiors. They
may also rise if there is excessive glaciation causing isostatic pressure in the mantle.
The rate of surface weathering can rise, resulting in an increase in the rate that organic
material is buried… and the formation of sedimentary basins.
The formation of a supercontinent
insulates the mantle. The flow of
heat will be concentrated,
resulting in volcanism and the
flooding of large areas with basalt.
Increased volcanism leads to
increased greenhouse gases, and
global warming. Notice here that
the hottest areas on the planet
are right over Pangea during this
period.
CAMP, or Central America Magmatic Province
Why didn’t the formation of the supercontinent
Rodinia influence the biosphere as much as
Pangea did?
How does mountain building due to continental
collision affect climate?
BIOSPHERE
Plate tectonics recycles water, carbon and
nitrogen, creating an environment that is
perfect for life.
Land and sea barriers generated by
continental drift have influenced distribution
of life on the Earth by restricting
movements of both plants and animals.
It makes oceans open and close, mountains
rise and fall and continents gather and split. Organisms that arose and diversified on an
ancient landmass, such as Gondwana,
were prevented by large sea barriers from
Every 500 to 700 million years, tectonics
colonizing other landmasses.
brings the continents together to form a
supercontinent.
Diversity of life is a consequence of
isolation. Less isolation, means less
When these supercontinents slowly break
diversification. This occurs during
up,
separating landmasses
forming
Breakup
Formationand
Breakup
of
shallow
seas, evolution
goes into
overdrive, supercontinent formation, producing both
of
of Pangea
Pangea
one continent and one ocean with one
Pannotiacountless new species which
forming
Panthalasacoast. Because genes (heritable units of
colonize the new habitats.
organisms) are allowed to “flow”, evolution
slows down.
Tectonics can move a continent from a
tropical to a polar latitude, where the
organisms will experience new patterns of
competition.
Break-up events result in the tremendous
proliferation of diversity of life forms. Gene
What does each of these
animals have in common?
Not only are they all marsupials, or special
mammals who birth embryos that are nurtured
within pouches, but they all are currently found
in the wild, only in Australia. They began
evolving near the breakup of the supercontinent,
Pangea, which went on to form Laurasia and
Wombat
Gondwana.
BIOSPHERE
During in the Triassic Period and later, the break
up of Pangea played a significant role in the
Devil
evolution of all marsupials, especially those in Tasmanian
the
Americas and Australia. They were unable to
compete in Asia and Europe, and became extinct
there.
Wallaby
Tectonics provides an explanation for the vast
number of different species of marsupials in
Australia, but the relative rarity of marsupials
elsewhere. Marsupials were able to adapt and
compete successfully only in Australia.
Evolutionarily, adaptation is what it’s all about!
Opossum: Only remaining
marsupial in North America
Formation of supercontinents often is accompanied by
_________ diversification of life forms, due to increased gene
flow.
Break-up of supercontinents leads to ___________ , which
influences huge diversification events.
What types of barriers do plate tectonics provide that influence
evolutionary events?
Why are there currently more marsupials on Australia than on any
other continent?
ATMOSPHERE AND HYDROSPHERE
Throughout the Pangea period, due to the reconfiguration of the continents and oceans,
global atmospheric circulation patterns changed. Atmospheric warming was caused by
Atmospheric Circulation:
expansion of magma beneath Pangea.
During Pangea
Carbon is cycled tthrough tectonics as well. Carbon
dioxide is released into the atmosphere by volcanic
activities. CO2 will warm up the air, and cause more
seawater to evaporate.
Acidic rain reduces the amount of CO2 by producing
carbon-containing minerals, which is carried into the
mantle by plate tectonics, and eventually returns to the
atmosphere through volcanoes to repeat the cycle
again.
Interestingly, this planetary self-help method of climate regulation may
not work very well if the CO2 released by human activities becomes too
much for the slow process of plate tectonics to handle!
During the time of Pangea, global circulation patterns were affected. When the
Australian and South American continents broke away from Antarctica approximately 38
mya, oceanic currents in the newly formed Southern Ocean created a circumpolar
current. This in turn led to atmospheric currents that rotated from west to east. Both
these atmospheric and oceanic currents stopped the transfer of warm tropical air and
water to the higher latitudes. This ultimately led to the cooling of the Antarctic continent.
HYDROSPHERE AND ATMOSPHERE
The thermal
plumes
that arise
during
As you saw on the last slide, there is an unavoidable
connection
between
atmospheric
supercontinent
in: When the
circulation, and oceanic circulation patterns. They
both affect buildup
climate result
greatly.
• warming
atmospheres,
results
North and South American continents joined around
3 mya
forming thewhich
isthmus
of in:
sea level
rise
due
thermal
expansion
Panama, (historically known as the Isthmus of•Darien)
this
had
thetoeffect
of stopping
water,
which
equatorial currents passing from the Atlantic toofthe
Pacific.
. results in:
It has been shown that this strengthened the Gulf • the melting of the ice sheets, changing
Stream by diverting more equatorial (warm)
the weight on the continents beneath,
currents northwards towards Europe.
changing isostatic pressure, which results
in:
In doing so, warm waters at high latitudes led to
• localized sea-level change as the land
increased evaporation and therefore atmospheric
rebounded with the removal of ice, which
moisture.
results in:
•increased precipitation as snow and ice
Today, evaporation in the tropical Atlantic and
Caribbean leaves behind saltier ocean waters and over Greenland, ultimately leading to a
puts fresh water vapor into the atmosphere.
build up of the ice cap, which results in:
• average albedo increase, which leads to
Trade Winds carry the water vapor westward
further global cooling.
across the low-lying isthmus, depositing fresh
This is cyclical in nature, as seen by this
water into the Pacific through rainfall. As a result,
graphic representation of global
the Atlantic is saltier than the Pacific
temperatures
through
geologic
timeapart.
Sea level is generally lower during the time of supercontinents,
and higher
when
they break
This is because the age of the oceanic lithosphere provides a major control on the depth of the
ocean basins, and therefore on global sea level. Let’s take a look at the cycle.
THE FUTURE
In the next 50 to 200 million years, all
of Earth’s continents will be once again
pushed together into a supercontinent.
The proposed supercontinent, Amasia,
will be centered around the North Pole.
This conclusion comes from a
computer model that shows the slow
movements of the continents over the
next several millions of years.
How will this supercontinent affect
global circulation patterns, and
climate? Will humans be here to see
it? Considering the fact that the
greatest mass extinction in Earth's
history happened at the same time
Pangaea formed 250 million years ago,
the formation of a supercontinent in the
future may eventually cause extinctions
on a similar scale.
The lessons from these vast geologic and
geographic changes is both simple and
exceedingly complex. As you’ve seen, the
opening and closing of seaways has a
profound influence on the distribution of fresh
water, nutrients, and energy in the global
ocean. The coupling of these changing oceans
with a changing atmosphere inevitably means
a changing climate.
Describe how CO2 is recycled in plate tectonics, and how it plays
a role in planetary temperatures.
What is the danger of increased human CO2 formation?
How did the break-up of Pangea, particularly Antarctica from
South America and Australia, lead to a colder climate for
Antarctica?
How does a strengthening Gulf Stream influence global
temperatures?
Which ocean is saltier, and why? When did this happen?
SATELLITE IMAGERY
Satellite imagery consists of
photographs of Earth made by means of
artificial satellites.
Satellite images have many applications
including meteorology, geology, forestry,
intelligence and warfare. Images can be in visible
The and
transceiver,
turn, relays
colors
in other in
spectra,
suchthe
as message
infrared. via a
Mt. Cotopaxi
satellite data link to a control centre onshore.
There are also elevation maps, usually made by
radar images. Interpretation and analysis of
satellite imagery is conducted using specialized
remote sensing applications. Some of the first
image enhancement of satellite photos was
conducted by the U.S. Government and its
contractors.
Satellite imagery is also used in seismology and
oceanography in deducing changes to land
formation, water depth and sea bed, by color
caused by earthquakes, volcanoes, and
tsunamis.
Satellite photography can be used to produce
composite images of an entire hemisphere
or to map a small area of the Earth, such
as this photo of the countryside of
Haskell County, Kansas, United States.
ARIEL PHOTOGRAPHY
Aerial photography is the technique of
capturing photographs of the land
from an elevated location. This type of
photography usually refers to
photographs which are taken when
the camera is not supported by a
ground-based structure. The camera
in aerial photography may be hand
held or mounted, and photographs
may be taken by a photographer,
triggered remotely, or triggered
automatically.
Aerial photography can produce some
very inspirational photographs that
provide us a beautiful view of our
Earth’s surface from a perspective
that we never see.
Unlike maps, which portray the physical
and cultural landscape with generalized
symbols and colors, aerial photography
reveals the terrain as it exists in nature. All
buildings, bridges, roads, urban and rural
areas, and other man-made features are
depicted as they were at the time of
photography.
Physical features, such as vegetation type
and distribution, river widths and courses,
shorelines, landslide areas, etc. are
shown with detail that no map can depict.
Aerial photography is extremely useful
both for site evaluation and for regional
analysis, as well as for historical
perspectives. It is used by engineers,
architects, city and regional planners,
geographers, geologists and historians.
How can we use infrared light in satellite imaging?
Describe passive vs. active satellite sensing.
Aerial photography can be accomplished both by an actual
photographer, or _____________, using robotics.
What are two positives of using aerial photography over some
other surface interpretation technique?
TOPOGRAPHIC MAPS
A topographic map, also known as a
topo map, is a map which shows
changes in elevation by using contour
lines.
Contour lines are imaginary lines that
join points of equal elevation on the
surface of the land above or below a
reference surface such as average sea
level. Contour lines make it possible to
show the height of mountains, depth of
the ocean bottom, (on a special topo
map known as a bathymetric map) and
steepness of slopes on a topo map.
To visualize what a contour line
represents, picture a mountain (or any
other topographic feature) and imagine
slicing through it with a perfectly flat,
horizontal piece of glass.
The contour interval is the
difference in elevation
between two adjacent
contour lines on a topo map.
You can determine the
contour interval by counting
the number of contours
between labeled index
contours and then by using
this formula:
For example, on the map
shown here, you can see
that there are 15 contour
lines between the 2400
index contour and the 1800
index contour. So the
contour interval is calculated
as follows:
Contour Interval: 40 ft.
Close line =Steep Slope
The steepest slopes on the map can be
seen by looking for lines that are very close
Contour lines bend upstream when crossing a
together. Since each line represents a
river
changepossible
in elevation
of a set
(20
Highest
elevation
of aamount
hillat the
Since contour
lines
must remain
same
meters
in
this
example),
lines
that
are
close
The
highestthey
elevation
a hill when
can bethey
calculated
elevation,
mustofbend
crossby finding
together
indicate
steepline
gradients.
The
area
the
last (highest)
contour
that hill,
andso
then
riverbeds.
A riverbed
dropsondownward,
thefiguring
circled
in red
very
steep,
because
has
out
the next
lineis
that
would
be drawn.
Theithighest
contour
line
must
bend
uphill
to
stay
at
the same
possible
elevation
of theclose
hill is just
below the value of
many lines
crowded
together.
elevation.
The
highlighted
lines
show
that
Depressions
are
shown
by
small
marks
that next line.
The
highest
possible
elevation
of the
the hill
direction
of
thearrow
Mill
must
be line
northeast.
pointingby
inward
offRiver
indicated
the
isthe
239contour
meters.
The
lineis
indicated
map is 220 meters.
TheThe
next
The last
arrow
pointingontothe
a depression,
or hole.
line
wouldline
be 240
(remember
that the contour
contour
withmeters
the marks,
or hatchers,
has the
interval
is 20 meters).
Since
is no
meter
line,
same elevation
as the
linethere
before
it.240
In this
case
the
the
hill
cannot
be
higher
than
239
meters!
hatchered line has a value of 140 meters, and the
depression must be less than 140 meters.
One of the most important sources of information on a topographic map is the date of
revision. Although large scale topographic features (such as mountains) take millions of
years to be formed and eroded, other features, such as volcanoes and river channels,
may change on a much more rapid scale.
• volcanic eruptions, flooding, landslides may alter topography significantly, roads
are added or go out of use, etc.
Present Day
GEOLOGIC MAPS
Geologic maps, like all maps, are designed to
show where things are.
•Unlike the maps we are used to which show
the distribution of roads or rivers or county
boundaries, a geologic map shows the
distribution of geologic features, including
different kinds of rocks and faults.
•A geologic map is usually printed on top of a
regular map (called a base map) to help you
locate your location on the map. The base map
is printed with light colors, so it doesn’t
interfere with seeing the geologic features on
the map.
•The geology is represented by colors, lines,
and special symbols unique to geologic maps.
The
most strikingthese
features
of geologic
maps you
are its
Understanding
features
will allow
tocolors. Each color represents
a
different geologic
A geologic
is a volume
of a certain kind of rock of a
understand
much unit.
of the
geologyunit
shown
in
given
age
range.
So a sandstone
one age might be colored bright orange, while
almost
any
standard
geologic of
map.
a sandstone of a different age might be colored pale brown.
Although the geology of
every area is different, all
geologic maps have several
features in common: colored
areas and letter symbols to
represent the kind of rock
unit at the surface in any
given area, and lines to show
the type and location of
contacts and faults.
The geology of an area has a
profound
effect onQalmany
things,
Holocene Period:
- Quaternary
alluvium
from the likelihood
landslides,
Quof
- Quaternary
undivided
Period:
Qt groundwater
- Quaternary terrace
toPleistocene
the availability
of
deposits
inCretaceous
wells, from
the
amount
of Chalk
Period:
Kau - Austin
Kef earthquake,
- Eagle Ford
shaking suffered in an
Kwb - Woodbine
to the presence of desirable
Kgm - Mainstreet & Grayson
minerals, from the way
theon map)
(undivided
Kpd - Denton,
Weno
Kpp landscape is shaped
to the
kinds
& Pawpaw
Pawpaw
of plants that grow best there.
Understanding the earth
underneath is the first step in
understanding the
world around
Kfd - Duck Creek & Kfw us. So what’s the geology
Fort Worth like in
Fort
(undivided on map) Worth
your neighborhood?
Kki - Kiamichi
Kgw - Walnut & Goodland
(undivided on map)
Kpa - Paluxy sand
___________ on topographic maps are lines that join points of
equal elevation.
One contour line is at 4,000 meters, and another, higher up the
mountain, is at 5,600 meters. There are 8 contours crossed
between the two. What is the contour interval?
On a contour map, the ___________ the lines are together, the
_____________ the slope.
Calculate the contour
interval on this map, in
meters, and determine
the highest possible
elevation of hill C.
How are depressions depicted on a contour map?
Why is the revision date on a topographic map of an area
depicting rivers and volcanoes more important than on
topographic maps showing other areas?
What feature makes it easier to interpret you location on a
geologic map?
Describe the geological foundation of our area, and determine
within which geologic period it was laid.