Transcript LPS Math-Science Partnership Grant

400 mya? or 700 mya
“split the difference”
550 mya
age of the Wichitas?
EXPECTATIONS
General comparison of the Wichitas to the
Ouachitas
 Geologic Time Scale
 Tectonic activity
 Activities:
record strike and dip
consider metamorphism
ecosystem change - elevation and rock
types
slope and terrain
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Geologic Time Scale

Eon (1 billion years; major division)
Phanerozoic Eon – (scientific) evidence of life
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Era (a major division of time)
Cenozoic Era (since the dinosaur)
Mezozoic Era (since the last “supercontinent)
Paleozoic Era (the Wichitas & the Ouachitas)
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Period (a subdivision of an Era)
Quaternary (since the last 2 million years)
includes the Jurassic Period
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Epoch (a subdivision of a Period)
currently in the Holocene Epoch
Plate Tectonics
The Divisions of Precambrian Time
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4.5 billion years ago, the Earth was born.
Comprehending that vastness in time is no easy
task. John McPhee, in his book Basin and Range,
recounts a nice illustration of what this sort of
time means. Stand with your arms held out to
each side and let the extent of the earth's history
be represented by the distance from the tips of
your fingers on your left hand to the tips of the
fingers on your right. Now, if someone were to
run a file across the fingernail of your right
middle finger, then the time that humans have
been on the earth would be erased.
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Nearly 4 thousand million years passed after the
Earth's inception before the first animals left their
traces. This stretch of time is called the
Precambrian. To speak of "the Precambrian" as a
single unified time period is misleading, for it
makes up roughly seven-eighths of the Earth's
history. During the Precambrian, the most
important events in biological history took place.
Consider that the Earth formed, life arose, the
first tectonic plates arose and began to move,
eukaryotic cells evolved, the atmosphere became
enriched in oxygen -- and just before the end of
the Precambrian, complex multi-cellular
organisms, including the first animals, evolved.
Was Pangaea the first?
Tectonic Activity
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The Earth's surface is made up of a series of
large plates (like pieces of a giant jigsaw puzzle).
These plates are in constant motion traveling at a
few centimeters per year.
The ocean floors are continually moving,
spreading from the centre and sinking at the
edges.
Convection currents beneath the plates move
the plates in different directions.
The source of heat driving the convection
currents is radioactive decay which is happening
deep in the Earth.
The edges of these plates, where they
move against each other, are sites of
intense geologic activity, such as
earthquakes, volcanoes, and mountain
building.
Divergent Boundaries
Continental crust begins to separate
creating a diverging plate boundary.
When a divergence occurs within a
continent it is called rifting. A plume of hot
magma rises from deep within the mantle
pushing up the crust and causing pressure
forcing the continent to break and
separate. Lava flows and earthquakes
would be seen. Lava flows and
earthquakes would be seen.
SLICES OF SCOTLAND
1998 year saw the agreement for
Scottish devolution. But in fact
Scotland and England have always
been different. The rocks from which
these two countries are made from
formed in very different parts of the
world and it was plate tectonics
which brought them together.
Oceans apart, although joined at the hip today, 550 million
years ago Scotland and England were both in the southern
hemisphere, separated by a vast ocean called the Iapetus.
To the south of the Iapetus Ocean lay the North American
continent including the rocks which now form England,
Wales and southern Ireland. 5,000 kilometres to the north
lay the American continent, and the rocks of Scotland. As
permanent as a large ocean may seem, they don't last
forever. About 500 million years ago both European and
American continents started to close in on each other.
Underneath the ocean, cold dense oceanic crust was diving
down under the lighter continental crust moving the
continents ever closer- the process is called subduction.
Slowly the Iapetus ocean began to shrink. Around 430
million years ago, the ocean had been squeezed out and
the continents collided. Scotland and England were fused
together. The seamless join occurs, rather amazingly, not
far from Hadrian's wall.
Piecing together the evidence - This is a
remarkable theory and you may be wondering
how can geologist tell all this happened.
Remarkable theories need remarkable evidence and that evidence certainly exists. Geologists
know the Iapetus Ocean existed because of
fossils called trilobites found in the rocks on
either side of the Scotland-England join. But
that's not all. The trilobites on the Scottish side
are totally different from those seen in England
and Wales. Why? It's thought that the width of
the Iapetus was far too wide for trilobites to
cross. Only when the ocean had shrunk enough
could trilobites swim across which is recorded
later on in the rock record.
Subduction is happening today under the
Pacific ocean, where crust is diving down
under Japan. The volcanoes found on
Japan are the result of the this
subduction. The melting crust forms large
underground vats of molten rocks called
magma chambers which feed the
volcanoes. If you look at a geology map of
Scotland you'll notice some large red
blobs. These blobs are granites. They
formed when the magma chamber cooled
and froze. The granites are further
evidence of the closing Iapetus ocean they were formed from the subducting
crust between 500 and 400 million years
ago.
Rucked Rocks - Perhaps the most convincing
clues to the crunching of the continents can be
found at St Abbs Head in south-east Scotland.
Exposures along the coast show rocks which are
tilted and folded. The rocks are called greywackes
are made of mud, silt and sandstones which
formed at the edge of the Iapetus ocean basin.
Geologists know they formed under water
because of structures found in the rocks. One
feature is that the fragments of rock from which
they are made are well sorted. The larger,
heavier bits sank quickly while the finer bits took
longer to settle to the bottom. Nearby rocks
contain marine fossils called graptolites which
floated in the ocean.
Originally the greywackes were laid down horizontally, but
today show spectacular folds. These folded rocks are found
over many tens of kilometers. What gave rise to such large
scale folding? Large scale mountain building forces. These
forces buckled and rucked the greywackes as the continents
came together.
The final evidence comes from the composition of the
Scottish rocks - they match those found in Newfoundland
today. Newfoundland was also part of the American plate
which collided together with the European plate. So how
come it's so far away now? Well, on a planet like ours
nothing stays still for long. Since the collision, further land
movements put play to our close encounter with America.
Slowly as the Atlantic ocean opened the American plate
drifted away, leaving behind a large chunk of rock which
today forms Scotland.
Convergent Boundaries
This is a convergent plate boundary, the plates move
towards each other. The amount of crust on the surface of
the earth remains relatively constant. Therefore, when
plates diverge (separate) and form new crust in one area,
the plates must converge (come together) in another area
and be destroyed. An example of this is the Nazca plate
being subducted under the South American plate to form
the Andes Mountain Chain.
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The plate moves downwards at a rate of a few centimeters
per year. The molten rock can take tens of thousands of
years to then either:
Solidify slowly underground as intrusive igneous rock
such as granite.
or
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Reach the surface and erupt as lava flows. Cooling rapidly
to form extrusive igneous rock such as basalt.
The floor of the Easter Pacific is moving towards South
America at a rate of 9 centimeters per year. It might not
seem much but over the past 10 million years the Pacific
crust has been subducted under South America and has
sunk nearly 1000 kilometers into the Earth's interior.
the Himalayas and Mount Everest
As the third example of plate movement, millions of years
ago India and an ancient ocean called the Tethys Ocean sat
on a tectonic plate. This plate was moving northwards
towards Asia at a rate of 10 centimeters per year. The
Tethys oceanic crust was being subducted under the Asian
Continent. The ocean got progressively smaller until about
55 million years ago when India 'hit' Asia. There was no
more ocean left to lubricate the subduction and so the
plates welled up to form the High Plateau of Tibet
and the Himalayan Mountains. The continental crust
under Tibet is over 70 kilometers thick. North of Katmandu,
the capital of Nepal, is a deep gorge in the Himalayas. the
rock here is made of schist and granite with contorted and
folded layers of marine sediments which were deposited by
the Tethys ocean over 60 million years ago.
Southern Oklahoma Aulacogen
Consortium for Continental Reflection Profiling - deep
reflection profiles recorded across the Wichita Mountains
and Anadarko Basin suggest that significant crustal
shortening occurred in the final stages of the evolution of
the Southern Oklahoma aulacogen.
The crystalline rocks of the Wichita Mountains were thrust
in Pennsylvanian time northeastward over sedimentary
rocks of the Anadarko Basin along a series of faults with
moderate (average 30° to 40°) and southwesterly dips.
These faults can be traced possibly as deep as 20 to 24 km.
Listric thrust faults and hanging-wall anticlines developed in the
sedimentary rocks of the basin. These features contrast with
conventional interpretations of Pennsylvanian structures as the
result of predominantly vertical movements along high-angle
faults, and they suggest that Pennsylvanian downwarping of the
Anadarko Basin was at least partially due to thrust loading.
Truncations of reflections from Cambrian-Ordovician rocks in the
deepest part of the basin suggest normal faulting, which would
support ideas of an early extensional stage in the aulacogen cycle.
The distinctive Precambrian layering seen on earlier COCORP data
recorded south of the Wichita Mountains cannot be recognized
under the Anadarko Basin, and the Proterozoic basin containing
that layering may have been bounded on its north side by a
Precambrian fault. This inferred fault was probably twice
reactivated during formation of the Southern Oklahoma
aulacogen—once during late Precambrian(?)-Early Cambrian
extension, and again during Pennsylvanian compression. The
popular view that aulacogens originated from radial rifting of
updomed, homogeneous continental crust is probably too
simplified, and a more important constraint on their location and
development may be the nature of pre-existing lines of weakness.
The Ouachita Mountains
The Ouachita Mountains are a Paleozoic orogenic belt across the
south-central portion of the United States. The Ouachitas are
surficial mountains in parts of Arkansas and Oklahoma, and
Ouachita structures are exposed in the Marathon Basin of West
Texas. In between, the Ouachitas are buried beneath Cretaceous
and younger strata. The Ouachita Mountains have much in
common with the Appalachian Mountains; the Ouachitas also have
their own unique aspects in terms of rock sequence and tectonic
setting. During the late Proterozoic and Paleozoic, the southern
margin of North America underwent a complete cycle of
continental rifting, ocean opening and closing, and collision that
created the Ouachita orogenic system. Initial rifting was along a
network of transforms and spreading zones from which failed rift
basins, called aulacogens, extended inland. From late Cambrian
through Devonian time, the continental margin was a passive
region of subsidence, where shelf sediments accumulated near
land and a deep ocean basin developed farther offshore.
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The Ouachita system displays the "starved
basin" phase of development from late
Ordovician through Devonian time.
Representative formations include the Big
Fork Chert, Arkansas Novaculite, and
Caballos Novaculite. These chert and shale
formations were deposited slowly in deep
water of a subsiding ocean basin. The
starved-basin phase represents the
maturing ocean basin following earlier
continental rifting and prior to subsequent
collision.
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Beginning in early Mississippian time, a dramatic
change in sedimentation took place, with rapid
accumulation of very thick flysch (turbidites) and
wildflysch (submarine landslides). Northward
thrusting of the continental margin culminated in
uplift of mountains by Pennsylvanian time and
draining of shallow inland seas during the
Permian. Crustal stress was transmitted into the
continental interior and resulted in local uplifts,
such as the Arbuckle Mountains, normal to the
Ouachita trend. The region was once again
subjected to continental rifting during Jurassic
and Cretaceous time, as evidenced by the Gulf
Coastal Plain sedimentary sequence and by
Cretaceous intrusive rocks
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The Ouachita orogeny is distinctive in that volcanism,
metamorphism, and intrusion are notably absent
throughout most of the system. The obvious interpretation
is that a subduction zone dipped southward beneath the
converging plate. By early Mississippian time, the Ouachita
basin had become a narrow trough into which a vast
amount of clastic and some (very little) volcanic sediment
was rapidly deposited from the south. Thrust uplift of this
material was the result of a collision with a continental
terrane that had been rifted from North America earlier.
This terrane underlies the Gulf Coastal Plain, over which a
great thickness of Cretaceous and Tertiary sediment has
accumulated on a slowly subsiding, passive continental
margin.
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The Ouachita Mountains are fold mountains like the
Appalachian Mountains to the east, and were originally
part of that range. During the Pennsylvanian part of the
Carboniferous period, about 300 million years ago, the
coastline of the Gulf of Mexico ran through the central
parts of Arkansas. As the South American
plate drifted northward, a subduction zone was created
in this region. The South American oceanic crust was
forced underneath the less-dense North American
continental crust. Geologists call this collision the
Ouachita orogeny. The collision buckled the continental
crust, producing the fold mountains we call the Ouachitas.
At one time the Ouachita Mountains were very similar in
height to the current elevations of the Rocky Mountains.
Due to the Ouachitas' age, the craggy tops have eroded
away leaving the low formations that used to be the heart
of the mountains.
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Unlike most other mountain ranges in the United
States, the Ouachitas run east and west rather
than north and south. Also, Ouachitas are
distinctive in that volcanism, metamorphism,
and intrusions are notably absent throughout
most of the system.
The Ouachitas are noted for quartz crystal
deposits around the Mount Ida area and for
renowned Arkansas novaculite whetstones.
This quartz was formed during the Ouachita
orogeny, as folded rocks cracked and allowed
fluids from deep in the Earth to fill the cracks.
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The Ouachita Mountain area of Arkansas is dominated by
Cambrian through Pennsylvanian clastic sediments, with
the lower Collier formation in the core of the range and the
Atoka formation on the flanks. The Atoka Formation,
formed in the Pennsylvanian Period, is a sequence of
marine, mostly tan to gray silty sandstones and grayishblack shales. Some rare calcareous beds and siliceous
shales are known. The Collier sequence is composed of gray
to black, lustrous shale containing occasional thin beds of
dense, black, and intensely fractured chert. An interval of
bluish-gray, dense to spary, thin-bedded limestone may be
present. Near its top, the limestone is conglomeratic and
pelletoidal, in part, with pebbles and cobbles of limestone,
chert, meta-arkose, and quartz. It was formed during the
Late Cambrian.
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The local rock formations are some of the
most distinctive in the state of Oklahoma.
Just north of Broken Bow, sedimentary
rock has been thrust upward due to an
ancient collision of the North
American and South American Plates,
forming what is now the Ouachita
Mountains. Evidence of what is called the
Ouachita orogeny can be seen all over
the park, where some layers of rock can
be seen tilted up at angles of about sixtydegrees. These geologic features can be
easily viewed around Broken Bow Lake
and Mountain Fork River, where
erosion has left much of the rock
exposed.
TEACHER GUIDE
to
OKLAHOMA LANDFORMS
and
OKLAHOMA ROCKS
PASS for Grade 8: Earth/Space Science
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Standard 4.1: Landforms result from
constructive forces such as crustal deformation,
volcanic eruption, and deposition of sediment and
destructive forces such as weathering and
erosion.
Standard 4.2: The formation, weathering,
sedimentation and reformation of rock constitute
a continuing “rock cycle” in which the total
amount of material stays the same as its form
changes.
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Places to see metamorphic rock in Oklahoma
While metamorphic rock is not common on the surface of Oklahoma’s landscape, there
are a few locations where it can be seen. Metamorphic rock is at the earth’s surface in a
couple of places at the eastern edge of the Arbuckle Mountains, north of Tishomingo.
A small band of metamorphic rock is also located in the Wichita Mountains, north of
Mount Scott.
One of the best places to observe metamorphic rock in Oklahoma is at, or near to,
Beavers Bend State Park, in southeast Oklahoma. Slate is present within the rock
formations that are exposed below the emergency spillway of Broken Bow Lake, as well
as on the east side of U.S. highway #259, 2.5 miles north of the south entrance to Beavers
Bend State Park.
A third location is about twelve miles west of Broken Bow, on the south side of state
highway #3, immediately west of the Glover River. Here the shale is actually a phyllite,
which is a variety of metamorphic rock that is an intermediate between a slate and a
schist.
PANGAEA
(Once? Twice? Three times? What about four times?)

During the late Proterozoic and Paleozoic, the
southern margin of North America underwent a
complete cycle of continental rifting, ocean
opening and closing, and collision that created
the Ouachita orogenic system. Initial rifting was
along a network of transforms and spreading
zones from which failed rift basins, called
aulacogens, extended inland. From late
Cambrian through Devonian time, the continental
margin was a passive region of subsidence,
where shelf sediments accumulated near land
and a deep ocean basin developed farther
offshore.
When did plants appear?
 435
mya – Silurian Period (seedless
vascular plants appeared)
Numerical Age
(continuation of geologic time)
 Radioactive
elements decay at a
constant rate (lab measurements)
 Isotopes – not all atoms of the same
element have necessarily the same
number of neutrons nor then the
same atomic weight (mass). Atoms
of the same element do have the
same number of protons.
 238U
is the symbolism for the
uranium nucleus (a nuclide) that has
238 neutrons and protons. This
number is referred to as the mass
number. All uranium atoms have 92
protons (atomic number).
 238U has then 92 protons and 146
neutrons
 Some
isotopes of a given element
are stable whereas others are not
stable (radioactive)
 Radioactive decay converts
(transforms) a radioactive atom into
another atom type that is not
radioactive – a different element
 The parent isotope is the atom that
undergoes decay
 The daughter product is the new
element that is formed
 For
example,
87Rb
40K
decays to
decays to
238U
87Sr
40Ar
decays to
206Pb
 Physicists
can measure how long it
takes for half of a group of parent
atoms to decay into daughter
products
 Half-life
of the isotope

Steps a geologist will take:
1. collect unweathered rocks
2. rocks are crushed and
appropriate minerals separated
from the rock debris
3. extract parent and daughter
atoms using an acid or a laser
4. samples are passed through a MS
instrument which uses a magnet to
separate the atoms by weight
 Can
sedimentary rock be dated using
radioactivity techniques? NO!
 Blocking temperature – While a
“rock” is warm (molten), atoms are
free to move about. One must wait
for the atoms to be locked into place
– the radiometric date is then
defined at the time the sample
cooled sufficiently to prevent atoms
from moving about [laying brick)
 Igneous
rock – results from molten
material
 Metamorphic rock – results from preexisting rock subjected to high
temperatures and pressures
 Sedimentary rock – the grains
comprising the rock can be dated
(time feldspar grains helped form the
rock) as to the time their parent
material formed. One cannot date
the time the sediment was deposited
 K-Ar
dating
 238U-Pb dating
 235U-Pb dating
 Rb-Sr dating
1.3 billion years
4.56 billion years
704 million years
48.8 billion years
Other numerical dating techniques
Fossil Index [guide fossils]
 Fossil assemblage
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law of faunal succession
principle of fossil succession
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Key beds
correlation
The Way The Earth Works
 Alfred
Wegener The Origin of the
Continents and Oceans (~1915)
 challenged geographic (geologic
permanence) ~ 1930
 continental drift hypothesis (Pangaea
– one land mass)
 Wegener lost his life while delivery
needed supplies to 2 weather
observers (party of 15) in Greenland
Evidence for Continental Drift
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Continental fit (Wegener viewed the earth
as dynamic and mobile, not immobile) – a
vast supercontinent, Pangaea, existed
some 250 million years ago, lasting until
some 65 million years ago
Today, it is considered that supercontinents formed and dispersed at least a
few times
Early as the 1500s, as Atlantic coastline
maps were develop, persons noticed the
alignment and fit of the continents
Glaciation (paleoclimatology) – Wegener
was an Artic meteorologist interested in
glaciers – direction of ice flow, deposition
of glacial till (mud, sand, pebbles, larger
rocks) – glaciers are found in polar
regions and high mountains today but
studies of till show that glaciers covered at
times large areas of continents (ice ages –
major ice age some 260-280 million years
ago))
glacial striations pointed outward from
southeastern Africa
During the Paleozoic Era, as the southern
continents straddled the South Pole, the
southern regions of North America, Europe
and the northwestern part of Africa would
have straddled the equator provide
tropical or semitropical climates ---- coal
deposits
What does one expect in the tropical
regions (tropical climates)?
coal deposition environments (Where do
we find coal beds today?)
reef development in the shallow seas of
tropical regions
deserts developed in the subtroical regions
(sand dune formation)
accumulation of salt deposits from
evaporating sea water
third clue - distribution of fossils
Why are there no polar bears in the
Antarctica? Kangaroos only in
Australia?
Glossopteris, Mesosaurus,
Cynognathus, Lystrosaurus
fourth clue – matching geologic units
wherein rocks of adjacent coastlines
matched (Appalachian Mt.)
fifth clue – paleomagnetism (since
1853 – Italian physicist) –
magnetism in ancient rocks (What is
magnetic declination?)
Curie point (~ 350 – 550 degrees
Celsius)
apparent polar wandering
A key  to undersatnding the
importance of continental drift
& sea-floor spreading