2013TectonicsofIndonesia_Lecture4

Tectonics of Indonesia

Lecture 4: Plate Tectonics and Magmatism

21.04.2023 Tectonics of Indonesian Region Lecture 4

World map showing plate boundaries (blue lines), the distribution of recent earthquakes (yellow dots) and active volcanoes (red triangles). Courtesy of NASA.

Active volcanoes on earth are located along the margins80% are on convergent boundaries

15% where plates diverge5% at intraplate ‘hotspots’


Plate tectonics and Magmatism

• At divergent boundaries• Intraplate magmatism• At convergent boundaries


Global hotspotsIntraplate mechanism and mantle plume hypothesis


Volatile Fluxing Mantle Wedge

Example: Merapi


More basaltic More andesiticstratovolcanoes


Primitive mantle melts Vs. Remelting of the lower crust


Volcano: Definition

• A vent at the Earth's surface through which magma (molten rock) and associated gases erupt, and also the cone built by effusive and explosive eruptions (USGS Volc.Program, accessed on 6 Oct 2013)


Types of volcanoes

• Shield volcanoes are relatively quiet, gently sloping, low viscosity magma (usually low in SiO2), largest in overall size, spews the least amount of gases Example: Kilauea

• Composite (or Stratovolcano) are explosive, steeply sloped, high viscosity magma, intermediate in size, intermediate gas content Example: Mt. St. Helens, Pinatubo, Mt. Merapi

• Cinder Cone volcanoes are somewhat explosive (not as much as Composite), have the steepest sloping, high viscosity magma, smallest in overall size, highest volcanic gases (another Cinder Cone picture) Example: Paricutin

http://volcano.und.nodak.edu/vwdocs/vwlessons/landforms/part1.html


http://www.satlab.hawaii.edu/space/hawaii/vfts/kilauea/kilauea.vfts.html




http://volcano.und.nodak.edu/vwdocs/msh/msh.html

http://volcano.und.nodak.edu/vwdocs/volc_images/southeast_asia/philippines/pinatubo.html


http://www.dc.peachnet.edu/~janderso/images/cindrcon.jpg

http://volcano.und.nodak.edu/vwdocs/volc_images/img_paricutin.html


Aspects of volcanic eruptions

• Pyroclastic Debris is the material ejected from an erupting volcano. Usually classified as (small to large) ash, cinders, blocks, and bombs

• Pyroclastic Flow (or fiery cloud) is a cloud of super-heated gas and ash that flows down slope from an erupting volcano. It can reach speeds of 100 mi/hr and has a temperature of ~800oC (hot enough to melt glass). It burns anything combustible.

• Volcanic Gases include CO2, CO, HCl, HF, H2S, SO2, H2, and H2O (many of these are toxic in sufficient concentrations)

http://volcano.und.nodak.edu/vwdocs/vwlessons/kinds/kinds.html

http://volcano.und.nodak.edu/vwdocs/msh/p_a/p_aa/p_aaa.html

http://volcano.und.nodak.edu/vwdocs/vwlessons/tephra/part3.html

http://volcano.und.nodak.edu/vwdocs/Parks/hawaii/Picture16.html

http://volcano.und.nodak.edu/vwdocs/volc_images/southeast_asia/indonesia/pyro.html



http://volcano.und.nodak.edu/vwdocs/Gases/measure.html

http://volcano.und.nodak.edu/vwdocs/Gases/measure.html

2013TectonicsofIndonesia_Lecture4

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