Comment: 05:47 - 06:58 (01:11)
Source: Annenberg/CPB Resources - Earth Revealed - 20. Running Water II: Landscape Evolution
Keywords: "William Morris Davis", geologist, uplift, erosion, landscape, modeling, "tectonic activity", "rock type", structure, climate, fold, fault, sand, clay, "Earth's surface", slope, "Grand Canyon", "sedimentary rock", weathering, arid, vegetation, canyon, time
Our transcription: In order to make his model easier for geologists to apply, Davis described uplift and erosion as events occurring separately in time, but he knew, in fact, these processes occur simultaneously.
Landscapes form by a continuous interplay of tectonic activity and erosion.
Other crucial elements also influence the shape of the land, including rock type, rock structure, and climate.
Solid rock, for example, can hold up a much steeper cliff than sand or clay, and when structures such as folds or faults appear at the Earth's surface, shapes adjust accordingly.
The slope of the Grand Canyon is a result of many of these factors.
The rocks are layered sedimentary strata with contrasting resistance to weathering.
This naturally results in slopes with differing steepness and rates of erosion.
In addition, the arid climate and relative lack of vegetation contribute to the sharp angular features of the Canyon walls.
Geology School Keywords