Erosion of Tahiti

As I stated in my previous post, Tahiti has quite steep terrain which is not typical of a shield volcano. What is typical, however, is the radial drainage pattern on the island (seen below).

 Radial drainage basins of Tahiti are apparent by the steep ridgeline
radiating out from the center of the main island.
(http://www.sciencephoto.com/media/97528/enlarge)

Tahiti receives 79 to 315 inches of rainfall annually attributing to constant erosion. This is evident by the islands deeply dissected gullies through which the rivers flow. The gullies started out as rills. The rills grew from the constant flow of precipitation that exceeded infiltration capacity or overland flow. Rainwater enters the drainage basins and into the rivers radiating from the center of the island.

Papenoo river carrying rainwater from the center of
volcano.

(http://svocelot.com/Landfalls/French_Polynesia/tahiti.htm)

The lush vegetation shown above displays how Tahiti has some
protection from erosion.
(http://www.tahitiexperience.com/Infopages/Society/TahitiFile.htm)

The island has steep slopes that aid the rivers in the alluvial transport of material. Erosion on some slopes are hindered by the vegetation from the lush tropical forests.

The capital city of Papeete continues to clear vegitation for the growth of the city.
(http://www.tahitisouvenirs.com/QsnEN.html)

Greater erosion occurs in the towns on the West side of Tahiti-Nui (above) and the croplands of the Taravao plateau (below). There is less vegetation to prevent erosion because of agriculture and construction efforts.

The plateau of Taravao is subject to erosion from agriculture. Also there are examples
of oxisol soils in the bottom left corner of the picture.
(http://www.daodao.com/Tourism-g309679-Tahiti_Society_Islands-Vacations.html)

High temperatures and high precipitation allow for the process of laterization. This process creates dark red soils composed of aluminum and iron. Laterization breaks down all other components of the soil like silica resulting in oxisol soil. The oxisols are very weak in nutrients for the vegetation (examples above and below). Instead the vegetation must quickly absorb nutrients through exposed roots, vines and large leaves.

Beautiful image of the lush vegitation as well as the oxisol soil of the road.
(http://www.weltrekordreise.ch/bilder%20pf/030-P1090560.jpg)

Tahiti also has histosols organic soils. Histosols are saturated with water most of the time and are dark in color. Histosols have more organic matter than oxisols but are not abundant on Tahiti. They can be found near sources of water (see below).

The waterfall has histosol soil on either side. Easy to find by
the black color.
(http://svocelot.com/Landfalls/French_Polynesia/tahiti.htm)

Tahiti has such a beautiful lanscape because of the thousands of years of erosion from rainfall. This has created an amazing land to explore and observe the beauty of nature.

References:
Ye, F., Sichoix, L., Barriot, P., & Dumas, P. (2010). Modeling the erosion of sheild volcanos: The tahiti case. Retrieved from http://www.interpraevent.at/palm-cms/upload_files/Publikationen/Tagungs
beitraege/2010__690.pdf

Allen, C. (n.d.). Geog 1202: Introduction to physical geography. Retrieved from http://clasfaculty.ucdenver.edu/callen/1202/