Exam 1 - GEOS1004

Chapters 1-5, 24

geology

science that examines Earth, its form and composition, and the changes that it has undergone and is undergoing (how earth works)

two areas of geology

physical and historical

physical geology

major division of geology, examines materials of Earth, seeks to understand processes and forces acting beneath and upon surface

historical geology

major division of geology, deals with origin of Earth and its development through time, usually involves study of fossils and their sequence in rock beds

when do natural processes become hazards?

when people try to live where geological processes occur

examples of geological hazards

earthquakes, volcanic eruptions, landslides/mudslides

Aristotle's impact on geology

views seen as authoritative for many centuries

catastrophism

James Ussher, concept that Earth was shaped by catastrophic events of short-term nature (mountains formed suddenly)

uniformitarianism

James Hutton, concept that processes that have shaped Earth in geological past are essentially the same as those operating today

geologic time scale

(try to remember)

how old is Earth?

4.6 billion years old

what assumption are all sciences based on?

the natural world behaves in a consistent and predictable manner that is comprehensible through careful, systematic study

what is the goal of science?

to discover underlying patterns in nature, use knowledge to make predictions about what should/not be expected

hypothesis

explanatory idea that may be correct but can be tested

speculation

explanatory idea that may be correct and testable

what must a hypothesis be?

testable and falsifiable; necessary consequences

necessary consequences

if this, then that

can some test be conceived to prove it false?

no outside of pure mathematics, you can never prove something to be true; all you can do is fail to prove it false

requirements of hypothesis

observations and ideas

what are observations?

evidence collected in facts

what are ideas?

explanations , speculations, theories

theory

explanatory idea that may be correct but has been extensively tested; well-tested and widely accepted view

does science move towards or away from theories?

over time, science moves TOWARDS theories; new ones are based off old ones

scientific method

process by which researchers raise questions, gather data, formulate, test scientific hypotheses (NO FIXED PATH)

steps of scientific method

raise a question, background research/collect scientific data, construct hypothesis, develop observations/experiments, analyze data, results, share

scientific misconceptions

• historical sciences aren't "real sciences" because no one was there to see things happen

• scientific ideas (speculations, hypotheses, theories) "grow up" to become scientific laws

• fact, law and theory all use unique terms

who decides where Mississippi River water flows go?

ethics, army corps of engineers (save Baton Rouge and New Orleans or Morgan City)

hydrosphere

water portion of Earth

atmosphere

Earth's gaseous envelope

geosphere

solid Earth

biosphere

totality of all plant and animal life

Earth system science

interdisciplinary study that seeks to examine Earth as a system composed of numerous interacting parts or subsystems

sources that power Earth

the sun (external, weather, climate, ocean circulation, erosional) and Earth's interior (volcanoes, earthquakes, mountains)

planetary geology

intersection of astronomy and geology; development of planetary systems, formation of planets, processes inside planets, processes on surfaces

most abundant elements in universe

hydrogen and helium

big bang theory

the universe originated 13.7 billion years ago from the cataclysmic explosion of a small mass of matter at extremely high density and temperature

where are heavier elements produced?

in stars or supernova (nuclear fusion)

describe the solar system

central star, eight major orbiting bodies (generally orbiting and rotating in same direction and plane), first four are rocky-last four are gaseous

nebular theory

model for origin of solar system, supposes rotating nebula of dust and gases contracted to form the sun and planets

describe the nebular hypothesis

1. cloud of dust and gas formed via gravitational attraction

2. cloud condensed

3. began to rotate

4. cloud becomes lumpy (central lump = star; smaller lumps = planetesimals)

5. planetesimals coalesce into planets --> planetary accretion

6. star ignites, heat cooks off gases nearby --> created planets

necessary consequences of nebular theory

1. gas and dust clouds in deep space

2. exoplanets, blocking distant starlight periodically (tug on then distant star)

3. some planetesimals still in system

4. accretion on planets (craters)

5. Earth should be compositionally homogeneous (whole Earth = 30% oxygen, crust = 46% oxygen)

are moon rocks older or younger than Earth's? meteories?

moon rocks are older than Earth's, younger than meteorites

describe the formation of the moon

1. middle/late stages of Earth's accretion (4.5 billion years ago), Mars-sized body impact Earth

2. debris from impactor and Earth expelled into space

3. impact sped up Earth's rotation and revolution

4. Earth reformed as molten body

5. Moon aggregated from debris

Earth's layers by chemical composition

core, mantle, crust

Earth's layers by physical properties

inner core, outer core, D'' layer, lower mantle, upper mantle, transition zone, asthenosphere, lithosphere

crust

Earth's relatively thin, rocky outer skin, consists of continental and oceanic crust

lithosphere

rigid outer layer of Earth, includes crust and upper mantle; where plate tectonic occur

asthenosphere

soft/weak layer of the mantle on which the lithosphere floats

transition zone

lowest portion of upper mantle

lower mantle

lowest portion of mantle, rigid rock

outer core

generates magnetic field, liquid layer

inner core

solid, due to immense pressure

characteristics used to determine processes that created a rock

composition and texture

major principal divisions of Earth's surface

ocean basins and continents

ocean basin

deep submarine region that lies beyond continental margins; basaltic rock

basalt

rock rich in dense iron and magnesium

continent

large area of land that includes adjacent continental shelf and islands that are structurally connected to mainland; thick, less dense, buoyant compared to ocean --> floats; composed of granitic rocks

continental margin

boundary between continental and oceanic crust (consists of continental shelf, slope, and rise)

deep-ocean basin

portion of seafloor lies between continental margin and oceanic ridge

mid-ocean ridge

undersea mountain chain where new ocean floor is produced; divergent plate boundary

who proposed continental drift hypothesis? how?

Alfred Wegner, circumstantial evidence

describe continental drift hypothesis

beginning 200 million years ago, supercontinent (Pangaea) began breaking apart into smaller continents, which then "drifted" to their present position

what is plate tectonics? what is it based on?

theory that Earth is shaped by moving lithospheric plates; based on Wegner's hypothesis of continental drift

what pieces of evidence of plate tectonics did Alfred Wegner provide to support his hypothesis, that ultimately led to the discovery of plate tectonics?

1. continental shelfs of South America and Africa fit together like jigsaw puzzle pieces

2. identical fossil organisms from Mesosaurus and Glossopteris found in South America and Africa

3. mountain belts of Appalachia are same in British Isles and Scandinavia; same igneous rock in South America and Africa

4. same glacial evidence in Africa, South America, Australia, and India; tropical swamps in North America, Europe, Southeast Asia

why were most geologists unconvinced by continental drift?

proposed tidal mechanisms for movement too weak, continental rock too weak to move through oceanic rock

what was the prevailing view of how land animals apparently migrated across vast expanses of open ocean?

rafting, island hopping, isthmian links (transatlantic land bridges)

lithospheric plates

rigid to mostly rigid segments of crust and upper mantle

how many lithospheric plates are there?

North American, South American, Pacific, African, Eurasian, Australian-Indian, Antarctic, Caribbean, Nazca, Philippine, Arabian, Cocos, Scotia, Juan de Fuca

where do most major interactions between plates occur?

along their boundaries, where most crustal deformation occurs

what generates Earth's magnetic field?

convection within liquid outer core, field lines pass through rock or iron filings

what direction do convection currents come out from to support magnetic field?

come out through south pole and into north pole

how are rocks and magnetism linked?

volcanoes erupt molten rock, iron rich rock cools, iron atoms line up with magnetic field lines

what does the tilt of the magnetic field tell us?

give us latitude; cooled rock traps in latitude and longitude

polar wandering

apparent movement of magnetic poles, magnetized rocks indicates that the continents have moved; proves continental drift

plate boundaries

plates move as separate and distinct units, defined by differences in behavior

divergent plate boundaries (aka spreading centers)

where two plates move apart, resulting in upwelling and partial melting of hot material from mantle to create new seafloor (mid-ocean ridges and continental rift valleys)

where are divergent plate boundaries located?

along crests of oceanic ridges

what exists at divergent boundaries?

volcanic activity, earthquakes from pulling apart

continental to oceanic rifting

continental masses break up, rift valleys become linear seas, linear seas fill and become oceans

oceanic ridge system

continuous elevated zone on floor of major ocean basins, 500-5000 km

seafloor spreading

Harry Hess, suggests new oceanic crust produced at crests of mid-ocean ridges, sites of divergence, 2 inches per year

convergent plate boundaries

where two plates move toward each other, resulting in oceanic lithosphere descending beneath overriding plate be reabsorbed into mantle OR collision of continental blocks to create mountain belt

what exists at convergent boundaries?

crust being recycled or thickened, may have volcanic activity, earthquakes from pushing together, develops from compressive forces

types of convergent boundaries

1. ocean-ocean (creates island arc, Alaska, subduction)

2. ocean-continent

3. continent-continent (Himalayas, Appalachians, Alps)

subduction

sideways/downward movement of the edge of a plate beneath another plate; oceanic = goes back into mantle

transform plate boundaries

where two plates slide horizontally past each other, no net change in crust, earthquakes from pushing past each other; found in oceans and continents

where are majority of transform faults located?

on ocean floor offsetting segments of oceanic ridge

preserved magnetism

occurs when magnetic minerals in lavas align their magnetic field with magnetic north, preserving record of pole's location at moment in time

passive boundaries

plates moving in same direction at same speed, no volcanoes and few earthquakes

what do passive boundaries create?

oil (sediments wash off land into ocean basin on shelf, plankton accumulated into sediments around oceans, combine)

how do plates move?

different directions, different speeds

mantle plume

mass of hotter-than-typical mantle material that ascends toward surface, may lead to igneous activity (located beneath Hawaii)

hot spot

concentration of heat in mantle, capable of producing magma extrudes onto surface (created Hawaiian Islands); most found in oceans

what moves the plates?

current thought is convection, heat sources from primordial and radioactive heat; heat from core transferred to lower mantle

convection

transfer of heat by mass movement or circulation of substance; warmer + less dense rise, colder fall, recycle

mineral

must be:

1. naturally occurring

2. inorganic

3. orderly crystalline structure

4. solid

5. characteristic chemical composition

rock

consolidated mixture of minerals

atom

smallest particle exists as an element; contain protons, neutrons, electrons

atomic number

number of protons in nucleus of atom, determines atom's chemical nature

element

substance that cannot be broken down into simpler substances