Blog Entry #2

More on Baengnokdam...

Baengnokdam, the lake that sits on top of Hallasan Mountain, came to be as a result of a caldera. The creation of a caldera begins with an excessive amount of pressure build up in a volcano, that causes the top blow off. Once the magma from the explosion channels back into the central vent the cone of the volcano gives in, leaving a hollow bowl at the top of the mountain; this catches rainfall and forms a lake. 

Image of Baengnokdam

The volcanic geography of JeJu...

Dragon Head Coast

Local preparing goods on coast of Dragon Head near sill formation

A sill is an intrusive volcanic land form that develops when magma forces itself between rock layers and solidifies horizontally. The image below of Dragon Head Coast in Jeju shows a formation to the left that is made up of sills that formed far beneath the surface and were exposed over time due to erosion. The sills shown here are the result of what was a basalt lava flow.  

Exposed intrusive volcanic land form in Jeju

Yongduam (Dragon Head Rock)

Yongduam off of the coast of Jeju City

Similar to the description above of intrusive volcanic landforms, dikes are also created by lava that flows beneath the surface and hardens. The difference is that dikes are created when magma flow solidifies vertically rather than horizontally. Eventually, just like sills,  dikes become exposed formations that appear on landscapes after erosion has occurred. The exposure of these dikes can be small or larger such as the Dragon Head Rock in Jeju. The hardened and exposed basalt lava flow in this image shows a dike that took on the shape of what appears to look like a “dragon’s head” as the title of the rock suggests. 

Diagram showing process of dike and sill formation

Images taken from:

http://www.panoramio.com/photo/51186294
http://www.deweyhammond.com/2011/04/yongmeori-dragons-head-coast-jeju-do.html
http://alokalekhana.wordpress.com/2010/07/01/yong-duam-dragon-head-rock/
http://taishan.chinadaily.com.cn/e/2009-12/21/content_9206687.htm
http://www.geology.um.maine.edu


Information taken from:
http://clasfaculty.ucdenver.edu/callen/1202
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/volcanic_landforms/title_page.html