Geography 101 Final

Sinkhole

Depression in earth's surface resulting from weathering of carbonate rock underground

Anthropocene

viewed as the period during which human activity has been the dominant influence on climate and the environment. Scientists believe that the extent of human environmental impacts is enough to cause a new geologic time period (epoch)

Island Formation at a Hotspot

(A) As the overlying plate moves over a stationary hot spot, it creates a chain of volcanoes Old volcanoes that have moved off the hot spot become extinct & are eroded & diminished in size. Eventually, the inactive volcanoes are moved into deeper water, where they become flat-topped seamounts (B) Hawaiian Islands were formed by a stationary hot spot. As the pacific plate moves over the hot spot, new islands are formed & old islands are moved into deeper water. The maximum ages of the islands are given in millions of years. The new island, named Lo'ihi, is forming & will rise above the sea in about 10,000 years

Hot Spots

1. Location at base of lithosphere where high temps cause the overlying crust to melt 2. Results from a mantle plume - a mostly stationary column of hot rock that extends from deep in mantle up to base of lithosphere

Evidence of Wegener's Theory

1. Matching Mountains & rock types The Appalachian Mountains in the U.S. are the same as the Atlas Mountains in Africa. Rocks in Greenland also match rocks found in Scotland & Norway If the Atlantic Ocean was closed up, all of these rock types would match up 2. Glacial Gravels Ancient tillities (rocks formed from glacial gravel deposits) in southern Africa, southern South America, India, southern Australia, & Antarctica suggest those continents were once joined & covered in ice. 3. The Geography of Fossils Geographically separated fossils of now-extinct organisms suggest formerly connected continents

Tectonic Settings for Igneous rock formation:

1. Mid-Ocean Ridges 2. Rift Valleys 3. Hot spots 4. Subduction Zones

The Rock Cycle

1. Rocks are formed, transformed from one type to another & recycled into the mantle 2. Rocks first form when magma cools and hardens (or freezes) into rock from a molten (liquid) state, either deep within Earth's crust or as lava extruded (pushed out) onto the earth's surface from a volcanic vent 3. Rocks can take any of several transformation pathways, depending on the tectonic setting where they are formed.

Oceanic-Oceanic Convergent Plate Boundary

1. Subduction: Oceanic lithosphere of one plate subducts beneath that of another plate 2. Deep-sea Trench: A deep-sea trench is formed where oceanic lithosphere subducts 3. Volcanic Island Arc: Subducting lithosphere partially melts into magma, which rises through the overlying oceanic lithosphere. The rising magma produces a chain of volcanoes that rise above the ocean's surface

Continental-Oceanic Convergent Plate Boundary

1. Subduction: Oceanic lithosphere subducts beneath the relatively buoyant continental lithosphere 2. Deep-sea Trench: A deep-sea trench is formed where oceanic lithosphere subducts 3. Accretionary Prism: During subduction, sediments & rock overlying the oceanic crust are scraped into an accretionary prism: (a folded & rumpled pile of sediments & rocks from sediments) 4. Buoyant Contient: The buoyant continent remains over the oceanic crust 5. Rising Magma & Volcanoes: Oceanic lithosphere and mantle material melt into magma, where they are mixed with seawater. This melted rock rises through the margin of the continental crust, creating a continental volcanic arc.

Current Model of Plate Tectonics:

14 major plates (7 primary & 7 secondary) move independently across the surface of the planet

Yellowstone Hot Spot

16 million years ago, oldest of extinct volcanoes on Yellowstone hotspot track were located over hot spot. Yellowstone's hot springs & geysers such as the Grand Prismatic Spring & Old Faithful are the result of the active magma body under the park.

Wegener's Continental Drift Theory:

300 million years ago, earth had one supercontinent Pangaea

Mineral Classes in Rock:

4 main rock-forming groups of minerals: silicates, oxides, sulfides, and sulfates, and carbonates

Fracking

A procedure where water, sand & chemicals are pumped under high pressure into shale bedrock to extract natural gas & oils trapped in the pores of the shale

Rock Sample Ages

Age of seafloor increases away from mid-ocean ridges. This pattern of older crust far away from ridges shows that crust forms at mid-ocean ridges, then moves away

crystallization

All minerals form through process of crystallization, which occurs when atoms or molecules come together in an orderly patterned structure called a crystal Mineral crystals have angular & flat surfaces

Recycled Lithosphere Cycle

As rocks are subducted, they can be melted into magma or transported deep into the mantle

Physical Weathering

Breakdown of rocks into smaller pieces (clasts) without altering the chemical makeup of the rock Physical weathering has greatest effect at high elevations and high latitudes (where temperatures routinely drop below freezing.) Cracks in rock (joints) provide surface areas on which physical weathering can act

Pros Of Fracking

Buys time while renewable energy technologies are developed Provides jobs, good for economy Natural gas burns cleaner than coal & reduces use of coal Reduces dependence on foreign oil

Carbonation

CO2 dissolves in water forming carbonic acid & reacts with carbonate rocks

2 Types of Crust:

Continental Crust: makes up continents, composed mainly of granite (forms from magma) Oceanic Crust: beneath the oceans, composed mainly of basalt (formed from lava)

Rift Valleys

Continental rifting allows mantle material to rise, decompress & form volcanoes at the surface

3 Principal Structures

Core, Mantle, Lithosphere

Dating Techniques used to determine abs. Age:

Dendrochronology - tree ring analysis Radiometric dating - assigning ages to materials based on radioactive decay of unstable elements in those materials

Dispensational Environments

Deserts & coastal sand dunes River floodplains Estuaries & lakes Coastal environments Offshore environments

mid-ocean ridges

Diverging oceanic crust allows mantle material to rise, decompress & melt into magma - creating mid-ocean ridges

Geologic Time

Earth is 4.6 billion years old Earth's history is divided into: epochs, periods, eras & eons based on major geologic events (like mass extinctions where at least 75% of all species go extinct) We live in the Holocene epoch (time period), nested in the Quaternary period in the Cenozoic era of the Phanerozoic eon.

Earth's Internal Structure

Earth's atmosphere, oceans & interior are arranged in layers that decrease in density away from earth's center

Principle of Uniformitarianism

Earth's physical systems operate under mostly gradual changes that accumulated over geologic time Catastrophic events occur intermittently, but uniformitarianism is constant.

plate boundaries

Earthquake activity reveals plate boundary locations (majority occur on plate boundaries)

Patterns of Magnetization

Every 200,000 years, for an unknown reason, Earth's magnetic field flips. North becomes south & south becomes north

Sedimentary Rock

Form only in depositional environment - places where sediments accumulate

Teton Range Wyoming

Formed when 40 mile long fault block was lowered, beginning about 13 million years ago Erosion by streams & glaciers subsequently cut into the higher block, removing most of the overlying rocks & creating a jagged mountain topography The Grand Teton is the highest peak in the range

Metamorphic Rock

Formed: by heat & pressure applied to preexisting rocks

igneous rock

Formed: cool from magma or lava

Sedimentary Rock

Formed: through cementation and compaction of sediments

Faulting

Fracture in crust where movement and earthquakes occur Occurs most often near plate boundaries, but regions far away from plate boundaries are also faulted Can create blocks of crust that move vertically relative to each other called fault blocks which creates mountains

Oceanographic Evidence of Plate Tectonics

Hess's theory (of seafloor spreading) & other evidence led to acceptance that plates move & a model showing how it's possible

Decompression Melting:

Is the melting of hot mantle material into magma as a result of pressure changes It occurs as mantel material is brought to a shallow depth in the lithosphere, where pressure on it decreases it enough to allow it to melt. Decompression melting occurs in three tectonic settings: mid-ocean ridges, rift valleys & hot spots. Decompression melting of the asthenosphere plays a prominent role in creation of new crust

mantle drag

Lateral flow of asthenosphere beneath plates creates mantle drag between asthenosphere & lithosphere above

Mantle

Layer of heated, slowly deforming solid rock that lies between base of crust & outer core

Lithosphere

Lithosphere Mantle: Earth's rigid crust & rigid lithospheric mantle extend to depth of 62 mi on avg. When subjected to stresses from moving asthenosphere beneath it, it cracks & breaks, forming lithospheric plates.

Igneous Rock Cycle

Magma cools deep within the crust. Lava cools on the crust's surface. Both form igneous rock.

Seafloor Bathymetry

Mapping seafloor with sonar revealed mid-ocean ridges. Sampling of rocks from these mountain ranges reveals volcanic origin (deep-sea trenches reveal oceanic-crust dives deep into mantel in the process of subduction)

Metamorphic Rocks

Metamorphic rocks can be metamorphosed more than once Result of metamorphism - is some transformation of the parent/ original rock

Cons of Fracking

Natural gas leaks & heavy machinery that run on diesel put carbon dioxide into the atmosphere, contributing to climate change Causes surface water & groundwater pollution & earthquakes at some locations Creates air pollution around drilling sites

Pangea

Pangaea was split apart as a result of convection in the asthenosphere beneath it. The split happened in 2 major steps (1) The opening of Tethys Sea and (2) opening of the Atlantic Ocean

Chemical Weathering

Process that changes minerals in a rock through chemical reactions involving water

How do plates move?

Ridge push mantle drag Slab pull

Hot Spots

Rising mantle plumes decompress and melt, resulting in hot spot volcanoes

Weathering and Erosion Cycle

Rocks are broken down into smaller fragments & chemically altered by weathering. Streams transport the weathered material downslope (mostly by flowing water) → the weathered material is deposited as sediments

Metamorphic Rock Cycle

Rocks can be crushed and heated, as they are in subduction and collision zones, to form metamorphic rocks

Subduction Zones

Seawater mixes with mantle material where oceanic lithosphere subducts, causing it to melt into magma

Sedimentary Rock cycle

Sediments are deposited by streams and lithified (turned to stone) through compaction and cementation, forming new sedimentary rocks.

Most common sedimentary rocks

Shale Sandstone Limestone

Silicates

Silicon & oxygen combine with each other & with other elements to form silicate minerals 95% of continental crust is formed from silicate minerals Rocks formed from silicates are structurally strong & relatively resistant to weathering.

Core

Solid inner core: made of dense elements (iron & nickel) Liquid outer core: made of liquid alloy of iron & nickel Circulating liquid metal in outer core generates electrical currents which create earth's magnetic field Magnetic north is not same as geographic north → magnetic pole moves about 34 miles/year Magnetic field forms magnetosphere which shields Earth from solar wind (stream of electrically charged particles emitted by sun)

Rejection of Wegener's theory

Some scientists rejected Wegener's idea because it conflicted with their conceptual model of the crust being fixed & impossible to move Scientific evidence supporting his theory came decades later & was re-named Plate Tectonics

"jigsaw-puzzle"

South America and Africa were combined, SA fits like a puzzle piece into Africa Wegener studied this

Weathering Rocks

Tectonic forces act sporadically across earth's surface, but forces that reduce vertical relief are present nearly everywhere on land and never rest

Appalachian Mountains

The Appalachians began folding 480 million years ago when the North American & African continental plates collide.

Plates of Lithosphere

The Lithosphere is broken into 14 major plates that move over Earth's surfaces and mantle beneath them convect.

Igneous Rocks - How do rocks melt?

The asthenosphere melts in 2 settings: where pressure on it is reduced or where water is mixed in

Slab pull

The weight of the subducting portion of the plate accelerates plate movement by pulling plate deeper into mantle

Flux Melting

This is another way mantle material melts into magma in subduction zones Process by which subducted water causes mantle material to melt by lowering its melting point

Kart Processes

Through the process of carbonation, acidic water reacts with the calcite in limestone causing dissolution (process in which minerals are dissolved in water & carried away) Areas with limestone bedrock form most widespread type of karst topography (form fastest in warm tropical regions)

Differential Weathering

Unequal weathering across a rock surface

Frost Wedging

Water trapped in the opening of rock freezes & expands, causing the opening to grow Where temperatures often drop below freezing, frost wedging is most important type of physical weathering When liquid water freezes to ice, it expands by almost 10%

transform boundary

Where one plate slips laterally past another Plate A (Divergent Plate boundary, mid-ocean ridge) moves away from Plate B alone a mid-ocean ridge The region between the two (now seperated mid oceanic ridge lines) is a transform boundary. A "scar" is formed by the former transform plate boundary

divergent boundaries

Where two plates move apart as new crust is formed Diverging plates create mid-ocean ridges that run almost from pole to pole Seafloor spreading As two plates diverge, new oceanic crust is continually added at a mid-ocean ridge. As the two plates diverge the ocean basin grows larger

convergent boundaries

Where two plates move toward each other

Folding

Wrinkle in crust from deformation caused by geologic stresses Occurs most often where 2 plates are converging, particularly in regions of subduction & collision Produces anticlines (fold in crost with an arch-like ridge) and syncline (fold in crust with U-shaped dip)

Absolute Age

an age that is specified in years (given in actual # of years)

Relative Age

compares age of one object or event with age of another, without specifying how old either is -- accounts for order of event

Intrusive Igneous Rock

cools from magma underground

3 Types of Plate Boundaries:

divergent, convergent, transform

Sulfides

form as sulfur combines with other elements Many sulfide minerals are ores of metals such as lead, zinc, mercury & copper

Carbonates

form when carbon combines with other elements, particularly oxygen Carbonate minerals often cement particles of sediment together to form sedimentary rocks One of the most common carbonate rocks is limestone

Oxides

form when other chemical elements combine with oxygen Ex: iron combined with oxygen forms the mineral hematite. Hematite gives many rocks a reddish color.

3 Rock Families

igneous, sedimentary, metamorphic

Weathering

is the process by which solid rock is dissolved and broken apart into smaller fragments Weathering → mass wasting → erosion

Dissolution

is the removal of bedrock through the chemical action of water Important weathering and erosion process for all rocks, but is particularly effective on carbonate sedimentary rocks

Denudation

lowering & wearing away of earth's surface Begins with disintegration of rock into smaller & smaller fragments Forces of weathering may physical or chemical

Ridge Push

magma rising along a mid-ocean ridge lifts oceanic lithosphere & forces it apart

Minerals:

naturally occuring, crystalline, solid chemical elements or compounds with a uniform chemical composition Minerals are abiogenic (not made by organisms)

Contact Metamorphism

occurs when rock comes into contact with and is heated by magma

Oxidation

oxygen atoms combine with minerals in rocks and weaken them

Karst Landforms

refers to an area dominated by the weathering of carbonate rocks, usually limestone.

Regional Metamorphism

results from the great heat & pressure found at convergent plate boundaries

Lithospheric Mantle

rigid and relatively brittle

Extrusive Igneous Rock:

rock that has cooled from lava on the crust's surface (volcanic rock)

Principle of Superposition:

sequence of rock layers forms as layers of sediments are deposited and harden into sedimentary rock → the principle of superposition states that in a sequence of rock layers, oldest rocks are at bottom, youngest at top.

Collapse Sinkhole

sinkhole formed where ceiling of a cavern has collapsed

Sinkhole Lake

sinkhole that has filled with water

Lower Mantle:

solid rock, but slowly deforms & flows in great circular convection loops (plastic)

Asthenosphere

solid state, but near melting, weak & easily deformed

Plate Tectonics

theory describes the origin, movement, and recycling of lithospheric plates & the resulting of landforms.

Mantle plume

thought to be rooted in earth's outer core, to remain mostly stationary & to rise at a rate of several cm per year

Erosion

transport of rock fragments by moving water, ice, or air

Black Triangles

used to show where one plate is moving toward another; the triangles point in the direction the plate is moving