Britannica
Sources used in this answer
How do lake sediments build up on the floors of rift valleys?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
tectonic basins and rift valleys
Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.
The floors of rift valleys are often relatively flat, a characteristic largely attributed to the accumulation of volcanic deposits and lacustrine (lake) sedimentation.1
Lake sediments build up on the floors of these valleys through several processes:
- Sedimentation: As streams and rivers enter the standing water of a lake within a rift, they are forced to deposit their load. Coarser materials like gravel and sand settle near the stream mouth, while finer silts and clays are carried further into the lake to settle as bottomset beds.2
- Drainage and Blocking: The formation of lakes in rift valleys is often influenced by geologic events, such as volcanic activity that blocks drainage patterns. For example, the eruption of the Virunga Mountains altered the drainage of Lake Kivu.3
- Climatic Influence: Fluctuations in lake levels, driven by climatic changes and precipitation, affect the extent of these water bodies and the subsequent deposition of materials along their shores and floors.3
- Filling of Relief: Over time, these fine-grained sediments can fill in and bury pre-existing relief, contributing to the characteristic flat floors of rift valleys.21