GEOS 550 Geology of National Parks- Review of Test #1
The Following highlighted parks have been discussed- the others have been briefly introduced
Passive
The Colorado
Ancient Rifts The Basin & Range Transform
Convergent
Margins
Plateau:
Boundary
Boundaries
Keweenawan Province:
Everglades NP Sunset Crater NM Rift
Death Valley NP
Point Reyes NS Devil's Tower
Biscayne NP Grand Canyon
Grand Tetons NP
Pinnacles NM
Yosemite NP
NP
Lava Beds NM
Sequoia-Kings
Petrified Forest
Canyon NP
NP
Devils Postpile NM
Olympic NP
Mt. Rainier NP
Shenandoah NP
Understand the following concepts and definitions:
The Structure of the Earth: Chemical layers (distinguished by chemical composition): (Listed from the inside
out) Iron core, Fe-Mg Silicate mantle, and Lighter Silicate crust. At any one point on the surface of the Earth, The
Crust is either oceanic (basaltic composition) or continental (granitic composition). Physical layers (distinguished
by physical properties); --do not coincide with chemical layers: (also listed from the Inside out) solid inner core,
liquid outer core, Solid mesosphere (= most of the mantle, lower part), plastic asthenosphere (within the upper
mantle), and rigid lithosphere (= uppermost mantle and all of the crust)
Plate Tectonics: Lithospheric Plates: The lithosphere is divided into plates. Each plate is a piece of lithosphere
which can include both continental and oceanic crust. Lithospheric plates move relative to each other, and seem to
be driven in their motion by convection in the asthenosphere. Plate Boundaries: The nature of the boundary
between two plates is affected profoundly by the relative motion between those two plates. Divergent boundaries
are those where two plates are moving away from each other and are characterized by basaltic magmatism. The
basaltic magma forms as the mantle material moves upward in the upwelling part of the asthenosphere convection
cell. The upward motion reduces pressure on the material and the already "slushy" material begins to melt, but only
the more silica rich parts, rendering a basaltic magma which is more silica rich than the parent material. New
oceanic crust is created when this basaltic magma cools and solidifies. Convergent boundaries are those where the
plates are moving together. Old Oceanic crust is destroyed or recycled at convergent plate boundaries through the
process of subduction, where one plate is subducted under another one and is returned to the asthenosphere. As
the plate descends, the increasing pressure (because it contains water) and heat cause it to melt--again, only
partially and the resulting magma is andesitic. If the over riding plate is continental at the boundary, then subduction
will form a mountain range dominated by volcanoes (Cascades, and the Andes). If the over riding plate is oceanic,
then an island arc (Aleutian Ranges) will form. A deep oceanic trench will form where the underlying plated is
subducted, and this trench will be on the same side of the island arc as the plate that is being subducted.
Continental material does not subduct under other materials because it is so light that it cannot sink under the much
heavier oceanic crust or the mantle.
Mantle Plumes or Hot Spots: Mantle plumes are small areas of upwelling mantle material. They orginate from the
core-mantle boundary where heat builds up, they rise up to the lithosphere, and stop. The plumes cause isolated
volcanic activity--one or a few volcanoes--in a sense punching hole in the overlying lithosphere. As a lithospheric
plate moves over the (apparently) stationary mantle plume, the volcanoes die, and the plumes forms a new center
of volcanic activity. Thus mantle plumes leave trails of volcanoes in the overlying plates, and by calculating the age
of these volcanoes we can tell both speed and direction of plate movement with respect to the mantle plumes.
Craton- Shields & Platforms-Geologic Stable Regions- Every continent has 1 or more. Canadian Shield, center of
North America around Hudson Bay Exposed by Pleistocene Glaciation Surrounded by Platforms. There are 11
Provinces- Superior, Wyoming, Slave, Nam, Hearne, Rae & Grenville, Wopmay. Based on Faults and Folds and on
ages of rocks. Boundaries marked by truncations in structural lineations and bands of severely deformed rocks. All
suture zones consolidated by 1.9 b.y. Know what cratons are as well as shield and platforms.
Some Questions to know:
 What is the structure of the Earth? How do we know?
 What do earthquake pattern tell us about the structure of the Earth and Plate Tectonics?
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Explain Plate tectonics and the different boundaries that exist, including hotspots and the parks and
monuments that illustrate these different boundaries.
Why is the upper part of the mantle included in the lithosphere?
Why do continents not subduct?
Explain what a lithospheric plate is and how many plates there are and their relative motions.
What is Continental Drift, who was Alfred Wegener and what evidence did he have for his idea.
Describe the plate tectonic setting of the Cascades and the coastal ranges.
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What are Minerals?
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What are Rocks?
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Igneous Rocks: magma, lava, intrusive and extrusive, high silica to low silica. What does grain or crystal
size of minerals in an igneous rock have to do with that rock's cooling history? Are large crystals indicative
of an extrusive or an intrusive rock?
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Igneous Rocks: Pyroclastics are volcanic rocks formed as magma is fragmented during an eruption. The
fragments of magma solidify in the air and fall as ash (dust sized particles); larger fragments can also form
including lappilli, the size of a pea, and volcanic bombs, which range upward from fist-sized. Other
Features: Columnar Jointing forms as lava flows (and some intrusions--Devil's Tower) cool and the
material contracts (Devil's Postpile).
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Sedimentary Rocks: sediment size, Sandstone, Siltstone, Shale, Limestone.
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Metamorphic Rocks: Types and origins of marble, quartzite, slate and gneiss.
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Geologic Structures: Know the different geologic structures and how to recognize them Folds- anticline,
syncline (etc) Faults: normal, reverse, thrust, strike-slip
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Horst & Grabens- how are normal faults produced by rifting be able to identify them
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Geologic Time Scale: The Eons, (Hadean, Archean, Proterozoic), The Eras: (Paleozoic, Mesozoic, and
Cenozoic). The Periods. AND the absolute age break between the eons and eras.
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Absolute Time: radioactive decay, half-life, isotopes and the different methods used to date rocks. What
rocks are best at obtaining dates for what methods?
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Stratigraphic Principles: original horizontality, lateral continuity, superposition, cross-cutting.
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Stratigraphic Concepts: Unconformities: nonconformity, angular unconformity, disconformity note: cite
examples from the Grand Canyon. Know the different types of unconformities as exemplified in the Grand
Canyon
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Formations --note: be familiar with the formations of the Grand Canyon Facies/Depositional
Environment. Understand Transgressions and Regressions. Know the sequence of formations in the
Grand Canyon that denote these transgressions/regressions.
A marine transgression is characterized by sea level rise (i.e. the shoreline moves toward higher ground),
resulting in flooding of the land. Transgressions can be caused by land subsidence or the filling of ocean
basins with water (due to melting of glacial ice). Transgressions and regressions may be caused by
tectonic events (orogenies), climate change or isostatic adjustments.
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Physiographic subdivisions of the coast (Coastal Plain, Continental shelf, Continental slope, Continental
Slope, Continental Rise, Abyssal Plain)
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Barrier Islands and how they are formed on passive margins. How sea level has fluctuated during the
Pleistocene and how it can change in the future.