‘ 지질학 ’ 이란 * 지구에 대한 연구 –From the Greek geo “earth” and logos “discussion” * 두 분야로 구분 – 일반지질학 (Physical geology) Study of the materials and processes of the earth both internal and surficial – 지사학 (Historical geology) Understanding the Earth’s complex history.

‘ 지질학 ’ 의 역사 고대 그리스 : – 주 관심 대상 : 보석, 화석, 화산 –Philosophers offered explanations. Aristotle( 아리스토텔레스 )’s explanations of geologic phenomena: –Earthquakes: Created when air crowded into the ground. –Fossil Fish: Some fish live motionless inside the earth and are found when people start excavating. Not based on experiments & observations. –Aristotle’s opinions were the accepted explanation during the Middle Ages.

‘ 지질학 ’ 의 역사 17 세기 중반 : –James Ussher ( 북아일랜드 대주교 ) constructed a chronology of the earth’s history. Used evidence from the bible. –Determined that the earth was created in 4004 B.C. –This age for the Earth was widely accepted amongst the religious and scientific community.

‘ 지질학 ’ 의 역사 격변설 (Catastrophism): –Was a strong influence on views of Earth’s history/creation in 17 th and 18 th centuries. –An attempt to fit observable landscapes to a relatively “young” earth. –Catastrophists believed that the Earth’s landscapes were primarily formed by great catastrophic events. Mountains created by great sudden upheavals. Other features created by disasters with no known cause.

‘ 지질학 ’ 의 역사 18 세기 후반 – 현대지질학 태동 –James Hutton in 1795, put forth concept of uniformitarianism ( 동일과정설 ) in his publication “Theory of the Earth”. –Uniformitarianism states “The physical, chemical and biological laws that operate today have also operated in the geologic past”. To understand ancient processes, we must understand modern processes. This is one of the major foundations of modern geology. –James Hutton suggested that the Earth was very old - several million years old.

Siccar Point

동일과정설 vs. 격변설 동일과정의 원리 – 긴 지구역사, 침식, 융기의 순환 격변설 –6600 만년 전 거대한 운석의 충돌 – 공룡의 멸종 –5 회 대량 멸종 (Mass Extinction)

You are here! Geology: The study of the Earth and its systems 태양을 농구공으로 가정한다면, 지구는 30m 떨어진 2.5mm 알갱이 토성은 300m 떨어진 2.5cm 포도 알갱이

Earth Systems F Atmosphere F Hydrosphere F Cryosphere F Geosphere F Biosphere

Earth System: Hydrosphere( 수권 ) & Cryosphere ( 빙권 ) –Encompasses all water: solid, liquid & gas. –Oceans cover 71% of the earth’s surface to an average depth of 3,800 m. - Glaciers, permafrost and ground ice Atmosphere( 기권 ) –Thin envelope of gasses around the planet. –On average 100 km thick. ½ of atmosphere is found within first 5.6 km. 90% of atmosphere is within the first 16 km.

Biosphere( 생물권 ) –Includes all life on Earth. –Concentrated between ocean floor and a few km into the atmosphere. Geosphere( 지권 ) –The solid Earth, extends from the surface to the center of the planet ~ 6400 km thick. –Not uniform. Earth System:

Atmosphere l Protection from Sun’s heat & UV rays l Weather: due to exchange of energy between Earth’s surface & atmosph. between atmosph. & outer space l Strongly interacts with surface Blanket of gases surrounding the Earth

Hydrosphere l Oceans (most prominent) 71% of surface of Earth l Streams, lakes, glaciers, underground water l Atmosphere Water portion of Earth

Cryosphere l Glaciers l Permafrost ( 영구동토 ) and ground ice l Polar ice caps l Frozen polar seas Icy portion of Earth’s crust

Biosphere l Earth’s surface and subsurface to depths of a few kilometers l Life occupies an extreme range of environments l Life strongly interacts with the atmosphere, the hydrosphere and the solid earth (these interactions are called ecology( 생태학 )!) Earth’s Ecosystems

지구 내부구조 crust mantle core Oceanic 5-8 km (“young”, < 180 m.y.) Continental km (older, up to 3.8 b.y.) Upper km Lower km Outer (liquid) km Inner (solid) km 3 distinct divisions:

Solid Earth lInterior of the Earth is losing heat. lPrimary source of heat: Radioactive decay ( 방사성 동위원소 붕괴 ) lHeat loss drives convection( 대류 ), based on density differences lHotter stuff is lighter and rises lCooler stuff is denser and sinks.

Earth’s dynamic interior and crust F Heat loss drives plate tectonics F Three types of plate boundaries 판구조론 (Plate tectonics)

지구의 생성 Planets thought to have formed: t At same time t From same material as the Sun Nebular hypothesis t Solar system formed from giant cloud of mostly hydrogen and helium, and a small percentage of heavier elements.

Nebular Hypothesis: States that the planets of our Solar System were formed by the “accretion( 부착 )” of materials from a cloud of gas and dust called a solar “nebula( 성운 )”. Collapse of the nebula under its own gravity formed a rotating disk around a dense, central core of material. This core eventually became hot enough to form the Sun.

Credit: Des Marais (2000) Humans arrive just a few seconds before noon.

Hazards of asteroids and comets

PlanetaryGeology World wide map of known impact structures

Meteor Crater, Arizona

Earth’s internal heat engine. Sources of heat energy: Early on- impact Later on- heat of radioactive decay Magma

Heat loss from the Earth’s interior drives plate tectonics

Plate Tectonics

Are there other Solar Systems with Earth-like planets in our Galaxy?

지구표면의 구성 Divided into two principle categories: - 대륙 Average thickness of crust: km Average elevation above sea level: 0.8 km Average density of rock: 2.7 g/cm 3 - 대양 Average thickness of crust: 7 km Average depth below sea level: 3.8 km Average density of rock: 3.0 g/cm 3

대륙의 주요특징 1 조산대 (Mountain Belts) –Uplifted regions of deformed rock. Rock look like they have been squeezed. –Indicate areas of collision. –Young mountain belts generally < 100 MY Primarily found in two areas: Around the Pacific Ocean Basin and stretching across Eurasia. –Old mountain belts > 100 MY Appalachians, Urals. No longer being built. Worn down by erosion. –Appalachians once higher than Himalayas.

대륙의 주요 특징 2 Stable Interiors –Extensive, flat, stable areas that have been eroded down (called cratons). Relatively stable for last 600 MY – 순상지 (Shields) Deformed crystalline rock. Form the stable centers of continents. Very old. Rock generally at least 1 billion years old. –Some are over 4 billion years old. – 안정적 대지 (Stable Platforms) Deformed crystalline rocks covered by layers of sedimentary rocks. –Sedimentary rocks generally horizontal except where the form basins & domes.

대양분지의 주요 특징 1 Continental Margins – Portion of seafloor adjacent to major landmasses. –Continental Shelf ( 대륙붕 ) – Gently sloping platform extending seawards from the shore. Can vary in width. –Continental Slope ( 대륙사면 )–Steep drop off extending from outer edge of shelf to deep ocean floor. Boundary between continents & deep ocean basin. –Continental Rise ( 대륙대 ) – Gradual incline from slope to deep ocean floor. Consists of thick layers of accumulated sediments from slope & shelf. Exists where there are no trenches.

Deep Ocean Basins – portion of seafloor between continents & oceanic ridges. –Abyssal plains – incredibly flat regions. –Deep-ocean trenches – Deepest part of seafloor (can be 11,000 meters deep). Narrow features. Often found adjacent to young mountain ranges or parallel to volcanic island arcs. –Seamounts – submerged volcanic structures. Sometimes form long chains. 대양분지의 주요 특징 2

해령 (Oceanic ridge) (mid-ocean ridge) – Most prominent feature of ocean floor. –Broad elevated feature. –Forms a continuous under-water mountain chain that goes through every ocean basin. –Consists of layers upon layers of fractured & uplifted igneous rock. Not deformed like rocks in continental mountain belts. 대양분지의 주요 특징 3

지구층상구조의 형성 Heat from the collision of material along with radioactive decay made early Earth heat up. Planet got hot enough that the accumulated material began to melt. Molten material began to separate according to density (chemical differentiation). –Heavy material such as iron & nickel sank towards center of the planet. –Lighter material such as silicon, oxygen & aluminum rose towards surface. Also allowed trapped gasses to escape & for a primitive atmosphere to form.

지구 내부구조 1 Layering can be defined either by –Chemical Composition –Physical Properties. Chemical Composition Layers: –Crust –Mantle –Core

지구내부구조 2 Crust – Silica & oxygen rich. –Lowest density layer –Two types of crust Oceanic: thin & more dense - 7 km thick, 3.0 g/cm 3 –Oldest rocks ~ 180 MY Continental: thick & less dense – 35 – 40 km thick, 2.7 g/cm 3 –Oldest rocks ~ 4.0 GY –Base of crust is called the Moho.

Mantle – Magnesium & iron rich. –Medium density layer Rocks are denser than crustal rocks –82% of earth’s volume is in the mantle. –~ 2900 km thick Core - Iron-nickel alloy (w/ very small amounts of sulfur) –Highest density layer ~ 11g/cm 3 –~ 3,400 km thick. –1/3 of earth’s mass is contained in the core, but it makes up only 1/6 of the volume. 지구내부구조 3

Earth’s Layers can also be divided by physical properties. –Does layer behave like a liquid or solid? –Is it strong or weak? Strength is based on the temperature and composition of the material One way the different physical layers can be seen is in the changes in velocity of seismic waves –S-wave velocities indicate how rigid the material is. Higher velocity = more rigid 지구내부구조 4

지구내부구조 5 Layers by Physical Properties: –Lithosphere –Asthenosphere –Transition Zone –Lower Mantle –D” –Outer Core –Inner Core

Earth’s Internal Structure Lithosphere ( 암석권 ) – Rigid solid. Uppermost physical layer. –Encompasses the crust and upper most portion of mantle. –Strong rigid layer –~ 100 km thick Can be up to 250 km thick under oldest portions of the continents.

Earth’s Internal Structure Asthenosphere ( 연약권 ) – Directly below the lithosphere. –Weak solid – material is solid, but the temperature /pressure conditions result in a little bit of melting. This “detaches” the lithosphere from the asthenosphere and allows it to move independently. –Extends from base of lithosphere to a depth of 410 km.

Earth’s Internal Structure Transition Zone ( 전이대 ) – Solid. Extends 410 km to 660 km in depth. –Top of transition zone is identified because suddenly density of material increases from 3.5 g/cm 3 to 3.7 g/cm 3. –Increase in pressure makes minerals in the rocks recrystallize into forms w/ tighter packed atomic structures. Olivine becomes β-spinel in the top part of zone. In lower part of the zone, β-spinel becomes an even tighter packed form: Ringwoodite (Ringwoodite is the high-pressure polymorph of olivine that is stable at high temperatures and pressures of the Earth's mantle between 525 to 660 km depth.)polymorpholivineEarth's mantle

Earth’s Internal Structure Lower Mantle ( 하부맨틀 ) – Solid. Extends from 660 km down to 2900 km –Largest layer. Makes up 56% of the entire volume of the earth. –Main mineral is perovskite an iron/magnesium silicate. –Density at bottom of lower mantle is around 5.6 g/cm 3

Earth’s Internal Structure D” – Layer at the bottom of the lower mantle. Solid. –Boundary between lower mantle and outer core. –Thickness is generally around a few hundred km. –Temperature and composition vary greatly in this layer. Evidence suggests there are areas of old subducted oceanic lithosphere and that is also the source of some mantle plumes.

Earth’s Internal Structure Outer Core ( 외핵 ) – Liquid iron. Extends from 2900 km to 5150 km. –Density increases dramatically from 5.6 g/m 3 (mantle) to 9.9 g/cm 3 Bigger density difference than between rock & air at Earth’s surface. – How do we know it’s liquid? Rapid change in seismic wave velocities. –P waves drop from 13.7 to 8.1 km/s when crossing the boundary. –S waves drop from 7.3 km/s to 0. S waves do not travel through outer core. Indicates it s a liquid. –Spinning of outer core is the source of the Earth’s magnetic field.

Earth’s Internal Structure Inner Core ( 내핵 ) –Solid Iron. Extends from 5150 km to the center of the earth (average depth is 6371km). – Other layers are shells, inner core is a sphere. –Temperatures are the hottest, but intense pressure keeps iron solid instead of liquid. –Recent data suggests the inner core spins faster than outer core & mantle. Laps them every few hundred years.

지각평형 (Isostasy) Just as a block of wood or iceberg floats in water, the crust floats on the mantle – this is the concept of isostasy. When the force of gravity pulling down = the force of buoyancy pushing up the crustal block is in isostatic equilibrium. The equilibrium line separates the submerged portion from the non-submerged portion.

What will happen if the iceberg melts? ~10% above equilibrium line ~90% below equilibrium line

지각평형 (Isostasy) Like the iceberg, the thickness of the crust is a factor in determining how “high” or “low” the crustal block floats on the mantle. – y.htmlhttp:// y.html

Isostasy Sedimentation, erosion, glaciers advancing / retreating, mountain building can all change the thickness of the crust. –Crust must then find new isostatic equilibrium. Crust undergoes isostatic adjustment – er6/GlacialIsostasy.htmlhttp:// er6/GlacialIsostasy.html

지각평형과 지표면 지형 Topography of Earth’s surface is related to the isostasy of the crustal blocks. –Shoreline = equilibrium line Continents sit high compared to the oceans. –Difference between average continental & oceanic elevation = 4.71 km –Due in part to differences in thickness of crust but also because of density differences. Granite islands in a “sea” of oceanic crust.