Chapter 1 Study Guide 10/10/2012
geology: “study of the earth”
physical: materials composing earth, seek to understand processes that operate beneath and upon surface
historical: origin of earth and development of planet through 4.6 billion year history
natural hazards only become hazards when people try to live where natural processes occur
physical environment divided into 3 major spheres: hydrosphere, atmosphere, geosphere
earth’s internal structure
compositional differences result in formation of 3 layers:
1) crus t: earth’s thin rocky layer
continental crust: 3570km, average composition of granodiorite
oceanic crust: 7km thick, dark igneous rock basalt
2) mantle : 82% of earth’s volume, solid, rocky shell. 2,900km
lithosphere: consists of entire crust and uppermost mantle. Forms Earth’s cool, rigid outer shell. 100km
thick and located 230km below oldest portions of continent. Detached from athenosphere and can move
independently. Rocks of lithosphere get progressively hotter and weaker as get deeper.
Athenosphere: soft, weak. 350km deep.
Lower mantle: 6602900 km. increase in pressure, mantle strengthen with depth.
3) core : ironnickel alloy, small amounts of oxygen silicon, sulfur
outer core: liquid layer 2,260km thick
inner core: iron solid, 1,216km thick
plate tectonics: earths rigid outer shell (lithosphere) broken into numerous slabs called lithosphere plates
and in continual motion.
plate movement driven by unequal distribution of heat within planet.
Convergent boundary: where 2 plates move together, one of the plates plunges beneath other and
descends into the mantle. Divergent boundary: located where plates pull apart. Fractures created as plates separate and filled with
molten rock that wells up from mantle. Hot material cools to form sea floor ridges
Transform sea fault boundaries: plates don’t push together or pull apart.
2 principle divisions of earth’s face are continents and ocean basins
Mountain belts primarily found in circum pacific belt and extends eastward from Alps through Iran,
Himalayas and into Indonesia.
Stable interiors of continents known as Shields and are flat regions made of crystalline rock.
Stable platforms are flat areas in the shield with highly deformed rocks that are covered by a thin veneer of
sedimentary rock .
Continental margin is portion of seafloor adjacent to major landmasses
Continental shelf: extends seaward from shore and underlain by continental crust and considered a flooded
extension of the continent.
Continental slope: relatively steep drop off that extends from the outer edge of the continental shelf to the
floor of the deep ocean. The boundary between the continents and deep ocean basins.
Continental rise: trenches do not exist, where steep continental slope merges into an incline. Consists of a
thick accumulation of sediments that moved down slope from the continental shelf to the deep ocean floor.
Deep Ocean Basins: located between the continental margins and oceanic ridges. Relatively narrow. Some
located adjacent to young mountains that flank continents and others are parallel linear island chains called
volcanic island arcs.
Abyssal plains: flat regions
Seamounts: submerged volcanic structures.
Volcanic activity also produce large lava plateaus.
Oceanic ridges: layer upon layer of igneous rock that has been fractured and uplifted
Earth as a system
closed system: no energy leaves or enters
open system: energy/matter flow into and out of system.
negative: work to inhibit change, maintain status quo
positive: enhance or drive change Chapter 7 Study Guide 10/10/2012
Continental Drift Theory Chapter 7 Study Guide 10/10/2012
1915, Alfred Wegner “Origin of Continets and Oceans”
single supercontinent consisting of all Earth’s landmasses once existed, Pangea. 200 million years ago
during early part of Mesozoic area the supercontinent fragmented into smaller landmasses.
Fit of South America and Africa and the distribution of fossils and ancient climates all seemed to buttress
idea that these now separate landmasses were once joined.
Shorelines are continually modified by wave erosion and depositional processes. Much better
approximation of outer boundary of continents is seaward edge of continental shelf.
1960, Sir Edward Bullard construct map that pieced together the edges of continental shelves of South
America and Africa at depth of 900m. The overlaps of map can be explained by continental stretching and
work of major river systems.
Fossil Match across the Sea
Identical fossil organisms discovered in rocks in South America and Africa.
Glossopteris: “seed fern” distribution which are too heavy to be carried by wind are found in Africa,
Australia, India and South America. Grow only in subpolar climates therefore must have been much closer
to South pole.
2.2 billion year old igneous rocks in Brazil that closely resemble aged rocks in Africa.
Mountain belt that includes Appalacian trends northeastward through eastern US and disappears off coast
of Newfoundland. Comparable mountains found in British Isles and Scandanavia.
Glacia period that had dated to Paleozoic era had beed discovered in southern Africa, South America,
Australia and India.
Weigner suggest configuration of southern continents joined together near south pole which account for
glaciation. Nothern continents closer to equator that accounts for tropical swamps that generate vast coal
mines in US, northern Europe and Asia. This was supported by the fact that the fern trees lacked growth
rings, a charecteristic of tropical plants that grow in regions having minimal yearly fluctuations in
Debate over Continetal Drift
Weigner propose that gravitational force of moon and sun were capable of gradually moving continets acrss
Also incorrecrlyt suggest that larger/sturdier continets broke through inner oceanic crust.
Plate Tectonics Chapter 7 Study Guide 10/10/2012
plate tectonics: uppermost mantle and the overlying crust behave as a strong rigid layer known as the
lithosphere which is broken into plates. The lithosphere overlies the weak athenosphere. The rigid outside
sphere is detached from the other layers which allow it to move independently.
Lithoshphere composed of 2 dozen segments having irregular shapes and sizes called lithospheric plates
or tectonic plates.
94% of earth covered by the N.American, S.American, Pacific, African, Eurasian, AustralianIndian and
intermediate plates carribean, nazca, phillipine, Arabian, cocos, scotia and juan de fuca
plates are in constant motion relative to eachother and most major interaction among them occur on plate
1)Divergent Boundaries: “constructive margins” where 2 plates move apart, result in
upwelling of hot material from matel to create new sea floor
2) Convergent Boundaries: “destructive margins” where two plates move together,
resulting in ocean lithosphere descending beneath and overriding plate, eventually
reabsorbed into mantle or possibly in collision of 2 continental blocks to create a
3) Trasnform Fault boundaries: “conservative margins” where 2 plates grind past
eachother without the production of destruction of the lithosphere.
located along the crests of oceanic ridges and can be thought of as constructive plate margins because
where new ocean floor is generated.
Also called spreading centers becaseu sea floor spreading occurs at these boundaries
Oceanic ridges: elevated ares of seafloor characterized by high heat flow and volcanism
Global ridge system is the longest topographical feature of earth’s surface
Rift valley is evidence that tensional forces are actively pulling ocean crust apart at ridge crest
Seafloorspreading is the mechanism that operates along the oceanic ridge system to create new sea floor.