Geology Of The Mekong River Basin

Patterns of internal drainage of the Mekong is unusual compared to other major rivers, the most important river systems that drain the interior of continents, such as the Amazon, Congo and Mississippi, have relatively simple dendritic tributary system that looks to a tree branch. Typically, such patterns develop in basins with gentle slopes where the underlying geological structure is rather homogeneous and stable, to little or no control over the river morphology. In contrast, the network tributary of the Salween, Yangtze, Mekong and especially the complex with various sub-basins are often different, and different types of drainage. These drainage systems have evolved in a complex environment where the underlying geology is heterogeneous and active, and is the main factor controlling the rivers and the landscapes they cut.

Height of the Tibetan plateau during the Tertiary period was an important factor in the legislative history of the southwest monsoon, which is the dominant climate influence the control of the hydrology of the Mekong Basin. Understanding the nature and timing of the share of Tibet (and in the Central Highlands of Vietnam) in order to help explain the origin of sediments to the delta and Lake Tonle Sap Great today. He studied the origin of sediments in the Mekong Delta to disclose the source of sediments in large clutch of about eight million years ago (Ma). Mon 36-8 mass (76%) of sediments deposited in the delta became the erosion of the bedrock Three Rivers area. 8 mA at stake, however, Three Rivers Area decreased by 40%, while the Central Highlands increased by 11-51%.

One of the surprising findings of the research farms of origin is a small portion of sediment from other parts of the Mekong basin, particularly the Khorat Plateau, northern highlands of Laos and northern Thailand, and the mountains south of the area Three Rivers.

The last ice age ended abruptly around 19,000 years ago (KA) when water levels rose rapidly, reaching a maximum of about 4.5 m above the present level of the Early Holocene at about 8 ka. At this point the coast of the South China Sea has almost reached Phnom Penh and the cores recovered near Angkor Borei contained sediments deposited under the influence of tides and marsh deposits of salt marshes and mangroves. Sediments deposited in Lake Tonle Sap Great around this time (7.9 to 7.3 ka) also shows signs of marine influence, suggesting a link to the South China Sea. Although the hydraulic relationship between the Mekong and Tonle Sap lake systems during the Holocene is not well understood, it is clear that between 9000 and 7500 years, at the confluence of the Tonle Sap and Mekong was in the immediate vicinity the South China Sea.

The current morphology of the river in the Mekong Delta evolved over the last 6000 years. During this period, the Delta advanced 200 km on the continental shelf in the South China Sea, covering an area of ​​over 62 500 km2. From 5.3 to 3.5 ka Delta advanced wide embayment formed between the higher ground near the border with Cambodia and the northern highlands of Ho Chi Minh City. During the development phase of the Delta away from the waves and currents along the shore has been built largely on river and tidal processes. Currently, Delta proceeded at a speed of 17-18 meters per year. After 3.5 ka, however, the delta was built in the embayment, and they came to wave action and sea currents. They bend to the deposition of the south-east of the Ca Mau peninsula, which is one of the newest features of the delta.

For most of the duration of the flow in the canals of the Mekong rock, or channels, which are limited or restricted by rock or old bed of the river flood and beaches. Geomorphological characteristics normally associated with the flooding of sections of mature rivers, such as bends, oxbow lakes, cut-offs, as well as extensive flooding is limited to a short stretch of the mainstream around Vientiane and Kratie, where the river valley to develop flood control channels are available free of charge created by the underlying rock.

Mekong Basin are generally not considered an active seismic zone, as the basin is covered by the relatively stable block of the continent. However, some parts of the basin in northern Laos, northern Thailand, Myanmar and China are experiencing frequent earthquakes and tremors. The magnitude of these earthquakes rarely exceed 6.5 on the Richter scale and is unlikely to cause damage.

Posted in: Mekong