Plate Tectonics Throughout the Solar System; The relationship to evolution of a planet, its climate, and vice versa

1. Plate Tectonics Throughout the Solar System; The relationship to evolution of a planet, its climate, and vice versa Claudia J. Alexander

2. Overview • What is Plate Tectonics? pg 3 • What are the elements of Climate? pg 11 • What does Plate Tectonics have to do with Climate? pg 22 • How does the system work on other Planets? pg 34 • A Unique aspect of Earth; the coupling of Geology, Climate, & Biology pg 71

3. Part 1, Plate Tectonics

4. The Earth is in motion.How can we tell? • Earthquakes • Seafloor spreading • volcanics • mountain building • motion of plates

5. All sorts of things move Ice Air Water The Earth’s Surface

6. Let’s review the Earth from Surface to Interior • Crust (hard) • Lithosphere (sort of soft) • Upper mantle (sort of soft) • Lower mantle (in motion) • Core (in motion) note: take a look at Windows ExploraTour on the Surface of the Earth

7. Convection • Convection is a familiar phenomenon in planetary science • ocean circulation • atmospheric circulation • Happens in response to (examples follow) • heating by the sun (exterior to Earth) • radioactive elements inside (interior to Earth) • atmospheric absorbers (interior to the atmosphere) • Convection is (only one) way in which a planets cools off.

8. The convective motion of the mantle drives the colder & harder crust, causing it to... • fracture into plates (hot chocolate phenomenon) • motion of the plates across the surface • subduction of the plates • Biproducts of this process include: • volcanics • mountain building • (crustal extension and deformation)

9. Magnetic Stripesacross the ocean floor • Hot lava comes out of the center of the ocean, at a mid-ocean ridge • Whatever the orientation of the Earth’s magnetic field, at the time this lava cools, is frozen into the cooling stone. • The magnetic orientations are either north (+) or south (-), whichever way the magnetic pole was pointed at the time. • Thus, as each new layer of material comes out of the spreading ridge and moves across the ocean floor towards the subducting trench, as time advances, stripes of changing magnetic polarity can be measured across the entirety of the ocean floor. subducting trench spreading ridge - + + -

10. Summary, part 1 What is plate tectonics? • The motion of plates of crust across the surface of the Earth It is caused by? • convective motions within the Earth itself It is measured by? • a striped pattern of magnetism across the floor of the ocean Other parts of the phenomena incude... • mid-ocean ridges where hot, fresh crust is produced • subducting trenches where cold, old crust is subsumed beneath the adjacent plate • movement of plates along fault lines (such as the San Andreas fault), often accompanied by earthquakes (but not always) • the building of mountains, island arcs, and volcanoes along the edges of the subducting plate • the creation of new crust (evolving composition), and fresh atomspheric constituents in the recycling of the old material

11. Part 2, What are the Elements of Climate? When you say climate, don’t you mean “Weather” - NO • Basic weather patterns • Hadley circulation • summer vs. winter • Obvious influences on climate • topographic forcing • air-sea interactions such as El Nino • alteration of the chemical composition of the air • volcanic eruptions • human pollution • Less-Obvious influences on climate • water cycle • other cycles (CO2) • chemical absorbers in the atmosphere • biogeochemical cycling

12. Summer vs. Winter • We all know that Earth is tilted 23˚ from the ecliptic. • This causes summer & winter differences. • Precession of the Earth’s orbit, however will affect the long-term climate of any particular region note: review Windows pages on Mars’ orbit

13. Topographic Forcing wet & rainy western Washington state • Hawaiian, or Colorado example of wet & rainy in regions before clouds pass over the mountains, dry in the lee of the mountain range • high topography forces clouds to empty their load before passing over • creation of “microclimates” dry eastern Washington state note: ExploraTour on the Surface of Earth

14. Martian bi-hemispheric situation • Mars has severe topographic differences between north and south • This induces a special weather pattern near the topographic high, Olympus Mons. note: take a moment to review the Windows ExploraTour on the Surface of Mars

15. El Nino & other air/sea oscillations • The Pacific Ocean is not level, and it can periodically be forced to “oscillate” from one side to the other (ENSO, or El Nino Southern Oscillation). [When the red in the map moves to the pacific coast of the American continent]. This can produce drastic changes in regional climate. • Other oscillations include • Arctic oscillation • NAO - North Atlantic oscillation

16. Injection of Foreign Particles Volcanic eruptions as well as human activity inject foreign particles and gas molecules into the atmosphere contributing to local and global increases or decreases in the greenhouse effect, sometimes with disasterous consequences. Some examples include: • 1879 Krakatoa explosion • global dust cloud & global cooling • 700 (?) Polynesian volcanic explosion • global dust cloud, global cooling, and European “dark” sky from 800 to 1000 AD. • Chixculub impact • global dust, global dark, wiped out the dinosaurs note: review Windows pages on specific volcanic eruptions

17. Changes in the population of greenhouse absorbers in the atmsophere - H2O • The Water Cycle • water and sediments are carried to the sea • water is returned to the atmosphere through evaporation • water is stored in glaciers (cold climate) • water is stored in the sea (warm climate) • lots of runoff (hard rock/soil) • no runoff (tundra) • Effects on climate (mixed): • more condensed water vapor in the atmosphere - increased cloudiness & increased warmth on the surface • increased frozen water and condensed water - increased albedo (reflectivity), reflecting the sun’s light away and reducing the warmth of the surface

18. Other greenhouse absorbers in the atmsophere - CO2 • The Carbon Cycle • CO2 is absorbed by water and made into rocks like calcite, limestone, and marble • CO2 is returned to the atmosphere through release from ocean depths, and by destruction of rocks such as in the burning of fossil fuels Calcite - a carbon mineral found in rocks and soils • Affects on Climate: • Increased storage in the atmosphere - YES • Increased storage at the bottom of the sea - No • Increased storage in rocks - No note: review Windows pages on Venus

19. Role of the Ocean • Surface waters absorb CO2. • When these waters are transported to colder regions they sink, and carry the CO2 with them • Thus large quatities of CO2 can be carried to the bottom of the ocean, and remain there for 1000 years. Reservoir for CO2

20. Biogeochemical Cycling • On Earth, the biosphere has helped take up some of the components of volatiles in the atmosphere, such as CO2 • (photosynthesis) • Constant recycling between rocks, volcanoes, and atmosphere, refreshes the sources of nutrients for the biosphere • (carbon, nitrogen, sulphur, and phosphorus) • On other planets, such as Venus shown here, there is no biosphere to assist with uptake of excess CO2, or retention of water. • On Venus, excess CO2 contributes to runaway greenhouse warming, creating an environment hostile to a terrestrial-like biosphere

21. Summary, part 2 What are some elements of climate? • Changes in (precession) a planets orbital characteristics • the distances of aphelion and perihelion, eccentricity of orbit • the tilt of the axis, & rotation rate • Forcing by topographic features • creates characteristics of local dryness or humidity • The relative location of large bodies of warm water (or cold glacial ice) • oscillations in the areas where warm water are located can change the climate drastically • the presence of glaciers can have a positive feedback effect - • namely they are bright and reflect more light, so they make a region even colder than before. • this means that if a glacier moves into an area, it can make the region colder and the glacier may grow • Changes in the abundance of greenhouse (absorbing) gases in the atmosphere, and/or injections of dust. • too much CO2 can be a problem • volcanic eruptions / asteroid impacts can cause climate changes • Global Ocean Circulation • The biosphere can affect the uptake of some critical volatiles • photosynthesis