Terrestrial & Planetary Tectonics Bert Vermeersen – TU Delft & Royal NIOZ Texel

1. Terrestrial & Planetary TectonicsBert Vermeersen – TU Delft & Royal NIOZ Texel

3. Eruption of Sarychev volcano (Kuril Island, NW of Japan) photo- graphed from the ISS

4. Positions of active volcanoes on the Earth’s surface

5. The “Ring of Fire” surrounding the Pacific

6. Positions of 29,000 earthquakes over a six-year time interval

7. Tectonic plates of the Earth and various types of plate boundaries

8. Comparison between geologicaly (NUVEL) and geodetically (GPS) determined plate motions Note the close agreement though time scales differ by more than a factor of one million !!!

9. Earthquakes discriminated by source depth

10. Ocean sea floor bathymetry reveals that hot mantle material wells up at mid-ocean ridges

11. At mid-ocean ridges upwelling decompressed basalt magmas (top) and hydrothermal vents (“black smokers”, right) can be observered from submersibles, indicating that two plates are being pulled apart.

12. Earthquakes discriminated by source depth

13. Process of subduction of old oceanic lithosphere near continental margins

14. Formation and subduction of oceanic lithosphere

15. Overview of global plate tectonics with various divergent and convergent plate boundaries

19. GOCE has captured how the super-continent Gondwanaland (Americas + Africa + India + Antarctica) 255 million years ago must have looked like, especially its west – east mountain range (blue ribbons = low density leftover roots of mountains eroded away in time) in this mosaic of shifting South America and Africa around and matching their coastlines. Courtesy: Carla Braitenberg

20. EROSION Low-density mountain root GOCE has captured how the super-continent Gondwanaland (Americas + Africa + India + Antarctica) 255 million years ago must have looked like, especially its west – east mountain range (blue ribbons = low density leftover roots of mountains eroded away in time) in this mosaic of shifting South America and Africa around and matching their coastlines. Courtesy: Carla Braitenberg

21. Earth’s gravitational gradient anomalies in the three different directions measured by the GOCE gradiometer. Panet et al., Nature Geoscience, 19 Jan. 2014, DOI: 10.1038/NGEO2063 Combined with seismic tomography, GOCE data might be the key to resolving one of the greatest uncertainties in modern-day seismology ….

22. The diffuse gravity gradient anomaly over North America (S1) corresponds to a seismic velocity anomaly between 900 and 1,600 km. This could be the remnants the Farallon Plate - an ancient oceanic plate that began subducting under the North American plate as Pangea broke apart (Panet et al., Nature Geoscience, 2014).

23. A third type of volcanism: hot spot tracks

24. Plume head Laboratory experiment of syrup drop released at the bottom of a water tank Plume tail

25. Hot spot volcanism: result of a mantle plume?

26. Deep origin of hot spots: tracks seem to run right through mid-ocean ridges

27. So the Earth has three types of (high-T) volcanism: • Two types related to plate tectonics: • mid-ocean ridge volcanism • subduction zone volcanism • and a third type related to mantle plumes: • ocean-island hotspot volcanism but this has not always been the case in Earth’s geological past and will not always be so in the future !

29. M O O N

30. Three views of Hadley rille, landing site of Apollo 15. The rille is over 120 km long. It is up to 1.5 km across and is over 300 m deep in places. Lava channels on Hawaii (right) are usually under 10 km long and are only 50-100 m wide.

31. Although the mare formed from large lava flows, there might be some evidence for explosive volcanism on the Moon, although impacts might be an alternative. In places, the lunar surface is covered by dark layers. They seem to mark areas where a thin layer has been draped over an older surface. Apollo 17 brought back samples from one such unit. They contain many small spheres of orange and black glass. These spheres probably formed from small drops of lava that cooled very quickly. Such droplets are thrown out of an eruption when gas bubbles burst near the surface.

32. M E R C U R Y

33. The smooth areas inside the larger craters in this photo of Mercury may be volcanic plains, somewhat like the maria on the Moon. There are many such smooth plains on Mercury.

34. Long-Wavelength Lithosphere Folding Byrna et al., Nat. Geosci., 7, 301-307, 2014 MESSENGER laser altimetry and stereo photogrammetry data indicate that the floors of craters have systematic tilts away from topographically high regions. Such tilted craters indicate that Mercury’s lithosphere has been affected by long-wavelength folding that might be associated with thermal contraction of Mercury (even up to 7 km?) at an early stage of its evolution.

35. V E N U S

36. Much of the volcanic activity on Venus occurs as basaltic eruptions that flood large areas. Venus has several large shield volcanoes, some of which are thought to be currently active. Recently announced findings indicate that Venus is still volcanically active, but only in a few hot spots. Maat Mons, the highest volcano on Venus, is 8 km high

37. Tectonics Earth: “Plate” Tectonics: Two Ideas 1) High surface temperatures Plates too ductile/buoyant to subduct Venus: “Plume” or “Blob” Tectonics: 2) No water Plates too stiff to subduct Current heat flow is less than internal heat production  interior heats up  models show that every few 108 yrs there might have been a catastrophic resurfacing event

38. M A R S

39. Mars is only about one-half the size of Earth and yet has several volcanoes that surpass the scale of the largest volcanoes on Earth. The most massive volcanoes are located on huge uplifts or domes in the Tharsis and Elysium regions of Mars. The Tharsis dome is 4,000 km across and has a height of 10 km. Located on its northwest flank are three large shield volcanoes: Ascraeus Mons, Pavonis Mons and Arsia Mons. Beyond the dome's northwest edge is Olympus Mons, the largest of the Tharsis volcanoes.

40. Olympus Mons is classified as a shield volcano. It is 24 km high, 550 km in diameter and is rimmed by a 6 km high scarp. It is one of the largest volcanoes in the Solar System. By comparison the largest volcano on Earth is Mauna Loa which is 9 km high and 120 km across.

41. A few provocativegeneralthoughtsto end with … • Observationsfromspace do notonlylearnussomethingabout present-daytectonics, but also - andsometimes even especially - about the past, alsofor the Earth • This is/has been the era of generalmappingmissions (gravity, altimetry, magnetism), even for the Moon andterrestrialplanets. Smart, dedicatedmissions (e.g. in terms of orbits, constellations) and “synergetic in design, instruments or operation” missionsmightgivefresh, new insights in solvingenduringproblems in tectonics • A most provocativethought: the problem on the truenature of HadleyRille on the Moon was solvedby “simply” sending a geologistwith a hammerandsupportedby a carto the Moon … andthisalreadymaybe even long beforeyouwere born?!