GEOL102.24p-Topic 1_Earth & Its Structure-1.pdf
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Topic 1: The Earth and Its Structure Source: NASA, Public Domain What's in a Smartphone? your smartphone isn't just a complex electronic device it's a gold mine,...
Topic 1: The Earth and Its Structure Source: NASA, Public Domain What's in a Smartphone? your smartphone isn't just a complex electronic device it's a gold mine, platinum mine, silver mine, copper mine..... Source: apple.com What's in a Smartphone? in fact, there are at least 75 different chemical elements in a smartphone... What's in a Smartphone? ... and all of the elements used to make a smartphone are obtained from the Earth (top 6 are below) lithium silicon aluminum gold copper iron "We set out to explore the moon and instead discovered the Earth." - William Anders, Apollo 8 astronaut Image Source: NASA, Public Domain The "Spheres" of the Earth Source: The Conversation includes the lithosphere, atmosphere, cryosphere, hydrosphere, and biosphere Components subsystems interact - mass and energy are stored of the Earth and transported between the components interactions between the subsystems determine how System climate varies in space and time Atmosphere contains layers of mixed gases Component Proportion (%) - major gases: nitrogen (N2) nitrogen (N2) 78.1 & oxygen (O2) oxygen (O2) 20.9 - minor gases: argon (Ar) & argon (Ar) 0.93 carbon dioxide (CO2) carbon dioxide (CO2) 0.035 - trace gases: methane (CH4) various trace gases 0.035 & ozone (O3) water vapour - the most common greenhouse gas along with CO2; varies from trace amounts to several % in local areas of the atmosphere Hydrosphere comprises all liquid water on Earth - oceans & continental water (lakes, rivers, groundwater) water covers ~70% of Earth’s surface source of the water vapour in the atmosphere ocean circulation strongly influences the Earth system Source: NOAA, Public Domain Cryosphere cryosphere - ice component of the Earth system - snow, lake and river ice, sea ice, glaciers and ice sheets, frozen ground and permafrost - stores ~75% of Earth’s fresh water Quttinirpaaq National Park, Ellesmere Island ice and snow reflect much of the solar energy that hits them - they have a high albedo (reflectivity) less ice and snow at Earth’s surface mean that more solar energy will be absorbed role of the cryosphere in the earth system best considered separately from the hydrosphere - have different roles Biosphere all ecosystems on Earth - amount and type of life at any location depends upon local climate conditions energy contained and transported by living organisms is quite small compared to the amount of radiation that reaches the Earth’s surface - e.g. photosynthesis uses < 0.1% of the sun’s radiation that hits a leaf Anthropogenic Effects humans (we are also part of the biosphere) also impact the Earth system, e.g. - release of greenhouse gases through industry, agriculture, other activities - altering surface albedo (reflectivity) of Earth (e.g. deforestation) Source: Getty Images Source: Romeo Gacad/AFP/Getty Images Lithosphere rocky outer shell of the earth includes land surface - a key component of Earth system - covers ~30% of Earth’s surface - absorbs and radiates (returns) solar energy stay tuned for a more specific geological definition Source: Grotzinger et al, Understanding Earth. 2014 Lithosphere Interactions Source: www.theclimategroup.org properties of land surface strongly influence the Earth system - e.g. water content, vegetation, topography, weathering processes increased land temperatures increase rate of water evaporation - transport of water vapour to atmosphere increases - increased cloud can reflect more solar radiation, cooling the earth negative feedback mechanism (decreases severity of change) Lithosphere Interactions - Weathering CO2 from the atmosphere is consumed during chemical weathering bicarbonate (HCO3-) produced during chemical weathering is transported to and stored in the oceans - formation of carbonate minerals (e.g., calcite) Figure 8.13 in Panchuk Hydrosphere Interactions 577,000 km3 of water evaporates from Earth’s surface annually - 87% from oceans - 13% from land (lakes and rivers) same amount falls as precipitation (rain, snow) annually - 79% on oceans - 21% on land changes in atmospheric temperature influence how much water vapour the atmosphere can hold (higher temperature, higher capacity for water vapour) Source: J. Mcbeth (2019) CC BY 4.0, map © 2019 Google Canada Cryosphere Interactions there is a seasonal exchange of water between cryosphere and hydrosphere - melting snow is a major annual source of freshwater - snowfall can account for significant proportion of total precipitation in some areas: ~27% in Saskatoon positive feedback mechanism (increases severity of change) to Earth system, e.g. - more energy absorbed at earth’s surface less ice & snow - if less ice and snow warms Source: http://www.ski-i.com/blog/ski-safety-tips-2/ surface more Photo: J. McBeth (2019) Biosphere Interactions plants interact with the atmosphere - absorb solar radiation and release heat - release water vapour through transpiration - absorb CO2, generate O2 (micro)organisms regulate atmospheric composition - produce or consume CO2 and methane (CH4) dissolved nutrients (e.g. N, P, Si, Fe, Zn) in the oceans feed plankton (base of the food chain) nutrient upwelling in ocean currents creates enhanced bioproductivity Example: How the “spheres” are connected (lithosphere) (cryosphere) (hydrosphere) (atmosphere) (biosphere) Figure 16.2 in Panchuk Summary – The Earth System earth system is composed of many "spheres" - lithosphere, atmosphere, cryosphere, hydrosphere, and biosphere atmosphere - layers of mixtures of gases hydrosphere - all liquid water: oceans, lakes and groundwater - ocean circulation strongly influences Earth system cryosphere (snow & ice) - different from hydrosphere - albedo (reflectivity) and loss of polar ice Summary – The Earth System biosphere - all living organisms - produce/consume water, CO2 + other compounds - anthropogenic effects lithosphere - landscape can affect Earth system - surficial weathering dissolved elements & nutrients, e.g. carbon cycle all subsystems interact feedback loops (positive, negative) climate varies in space and time Note: This course will not cover all of the material in Suggested Readings each chapter of the textbook. These reading recommendations highlight material relevant to this Textbook course. Chapter 16 Introduction Section 16.1: What is the Earth System? Section 16.5: Humans in the Earth System Workbook Chapter 16 - vocabulary and review questions Source: geologypage.com "geo" (Earth) + "logia" (study) = the study of the Earth describes the structure and composition of the Earth and the processes that have shaped it through time The Structure of the Earth Earth’s layers: crust, mantle, core (inner and outer) The layers of Earth (Credit: www.phys.org) Layered Earth Crust Solid, 0-40 km, 0.4% of mass Mantle Solid, 40-2890 km, 67.1% of mass Outer Core Liquid, 2890-5150 km, 30.8% of mass Inner Core Solid, 5150-6370 km, 1.7% of mass Source: Grotzinger et al, Understanding Earth. 2014 Layered Earth Crust 2.8 g/cm3 silicates Mantle 4.5 g/cm3 dense silicates, oxides Outer Core 10-12 g/cm3 Inner Core ~13 g/cm3 iron-nickel alloy Source: Grotzinger et al, Understanding Earth. 2014 8 elements account for about 99 wt. % of Earth http://commons.wikimedia.org/wiki/File:Periodic_table_(polyatomic).svg Review workbook appendix on chemistry: https://openpress.usask.ca/geolworkbook/back-matter/appendix-i-chemistry/ But how do we know? Earth’s Composition has been inferred (determined from evidence) from: - seismic studies - study of earthquake waves moving through the Earth (geophysics) - knowledge of Earth’s overall (average) density - samples of the Earth’s crust and mantle and meteorites Source: Fletcher et al. (2014) Introduction to Physical Geology Layered Earth Crust Solid, 0-40 km, 0.4% of mass Mantle Solid, 40-2890 km, 67.1% of mass Outer Core Liquid, 2890-5150 km, 30.8% of mass Inner Core Solid, 5150-6370 km, 1.7% of mass Source: Grotzinger et al, Understanding Earth. 2014 Two Types of Crust crust is not homogeneous, it is also layered mainly due to differences in density less dense continental continental crust is less crust "floats" on denser mantle dense than oceanic crust oceanic crust continental crust (3.0 g/cm3) (2.8 g/cm3) mantle "Moho" (3.4 g/cm3) Continental vs. Oceanic Crust oceanic crust continental crust (3.0 g/cm3) (2.8 g/cm3) mantle "Moho" (3.4 g/cm3) continental crust - enriched in minerals (e.g. feldspar and quartz) with lighter elements, e.g. K, Na, Al, Si "felsic" oceanic crust - enriched in minerals composed of slightly heavier elements, e.g. Mg, Fe "mafic" boundary between the crust (continental / oceanic) and mantle is called the Mohorovičić discontinuity ("Moho") Layered Earth Crust Solid, 0-40 km, 0.4% of mass Mantle Solid, 40-2890 km, 67.1% of mass Outer Core Liquid, 2890-5150 km, 30.8% of mass Inner Core Solid, 5150-6370 km, 1.7% of mass Source: Grotzinger et al, Understanding Earth. 2014 Mantle earth's mantle can be further subdivided into the upper and lower mantle within the upper mantle, two important subdivisions - uppermost mantle (solid and rigid) - semi-molten (partially melted) mantle "asthenosphere" = soft, ductile, viscous layer ~180 km thick just below uppermost mantle Source: USGS Lithosphere & Asthenosphere "lithos" = stone (Greek) "asthenos" = weak Lithosphere vs Crust: an orange peel analogy crust: orange peel (rigid) uppermost mantle: white peel (also rigid) upper mantle: white peel + Source: USGS squishy orange "lithosphere" = uppermost mantle + crust - rigid layer asthenosphere: squishy orange underneath lithosphere: whole peel (orange + white) (rigid) ~100 km thick Orange Peel ©2017-2018 Margarita Morrigan Temperature gradient in the Earth Source: Karla Panchuk (2018) CC BY 4.0, modified after Steven Earle (2016) CC BY 4.0 Why is the Earth's interior so hot? radioactive decay “primordial heat” - residual heat remaining from when the Earth first formed Source: Karla Panchuk (2018) CC BY 4.0, modified after Steven Earle (2016) CC BY 4.0 Rocks in the asthenosphere are moving Source: USGS in the asthenosphere, rocks are plastic (ductile) and can convect (move in a loop, hot rocks rising, cool rocks sinking) similar to boiling water in a pot or heating air in a convection oven except much more slowly! Mantle Plumes ("Hotspots") columns of hot magma rise from core-mantle boundary (base of mantle) volcanism in Hawaii is thought to result from a mantle plume Source: Fletcher, Gibson & Ansdell (2014) Introduction to Physical Geology Layered Earth Crust Solid, 0-40 km, 0.4% of mass Mantle Solid, 40-2890 km, 67.1% of mass Outer Core Liquid, 2890-5150 km, 30.8% of mass Inner Core Solid, 5150-6370 km, 1.7% of mass Source: Grotzinger et al, Understanding Earth. 2014 Earth’s Magnetic Field generated by convection in liquid outer core Source: Fletcher, Gibson & Ansdell (2014) Introduction to Physical Geology Summary - Structure of the Earth layered Earth - layers have different compositions - crust, mantle, core each layer has different properties (e.g., density, physical state (liquid/solid) a handful of elements account for ~99 % of Earth's mass - crust: enriched in lighter elements, e.g. Si, Al - core: concentrated with heavier elements, e.g. Fe, Ni each layer is also inhomogeneous - crust: continental crust ("felsic"), oceanic crust ("mafic") - mantle: upper mantle, lower mantle; ductile & rigid layers - core: outer (liquid, earth's magnetic field), inner (solid) Summary - Structure of the Earth lithosphere - Earth’s crust + uppermost mantle - acts as a solid and rigid "plate" asthenosphere - soft, partially molten, viscous layer in the upper mantle - just underneath the lithosphere temperature generally increases with depth into the Earth "geothermal gradient" rocks in the Earth’s mantle (asthenosphere) convect mantle plumes - columns of hot magma that rise up from base of mantle through the crust (e.g. Hawaii) Note: This course will not cover all of the material in Suggested Readings each chapter of the textbook. These reading recommendations highlight material relevant to this Textbook course. Chapter 3 Introduction Section 3.1: Earth’s layers: Crust, Mantle, and Core Section 3.3: Earth’s Interior Heat Workbook Chapter 3 - vocabulary and review questions Additional Materials: The Earth & Its Structure 13 Misconceptions About Climate Change - an amusing 7-minute video highlighting some misconceptions about climate change The Discovery of the Earth's Layers - a 6-minute video explaining how the Earth's layers were discovered, and what they are Additional Materials: The Earth & Its Structure Why Does the Earth Have Layers? - a short video explaining how scientists think the Earth originally formed and why When Did the Continents Form? - an easy-to-read-article looking at the linkages between the Earth's internal structure and the Earth system, and when we think the first continents appeared in the early history of the Earth Bad Geology Movie summary: an unknown force has caused the earth's inner core to stop rotating. With the planet's magnetic field rapidly deteriorating, Earth's atmosphere literally starts to disintegrate with catastrophic consequences. use your knowledge to find all of the reasons why this Hollywood blockbuster is not https://en.wikipedia.org/w/index.php?curid=3772912 geologically sound!
