Interlude F: ever-changing landscapes and the
hydrologic cycle.
F.1 introduction
¤ Landscape: the character and shape of the land surface in a region.
¤ Landforms: the individual shapes (such as valleys, clifs, fans, mesas and beaches) that make
up landscapes.
¤ The hydrologic cycle: the contnual passage of water from reservoir to reservoir in the Earth
system.
F.2 Shaping the Earth’s surface
Uplift and subsidence; erosion and deposition
Uplift: relatve upward movement of a region
¤ Thickening of the crust
¤ Heatng of the lithosphere
¤ Rebound due to unloading
¤ Delaminaton (dense lithospheric mantle separates from the base of the plate and sinks)
Subsidence: relatve downward movement of a region
¤ Thinning of the crust due to stretching
¤ Cooling of the lithosphere
¤ Sinking due to loading
Topography: variaton in land-surface elevatons. Can be represented on a topographic map, or by
shaded-relief map, conveys the impression of three dimensions by shading appropriate slopes to
appear as if they are in shadows cast when the sun is low in the sky.
Digital elevaton map (DEM): a computer-produced portrayal of elevaton diferences commonly
using shading to simulate shadows; the data used to produce the map assigns elevatons to each
point on the map.
Relief: the elevaton diference between two points separated by a specifed horizontal distance on a
map. We can speak of a high-relief by big diferences and a low-relief by small diferences.
When relief develops various components to modify and shape the Earth kick in. Rock at the uplif or
just near it, weathers, fractures and weakens. On a slope this becomes a downslope movement: the
gravity-driven tumbling or sliding of debris from higher elevatons to lower ones. In additon this
causes erosion: the grinding away and removal of the Earth’s surface. And when moving fuids slow
down, depositon of the transported sediment takes place. Downslope movement, erosion, and
depositon redistribute rock and sediment, ultmately stripping it from higher areas and collectng it
in lower areas.
Rates of uplif and subsidence range between 0,01 and 10 mm per year. Erosion can carve out
several meters of substrate: the material just below the ground surface, in a single foodd storm or
landslide. The depositon of such an event can accumulate meters of debris.
hydrologic cycle.
F.1 introduction
¤ Landscape: the character and shape of the land surface in a region.
¤ Landforms: the individual shapes (such as valleys, clifs, fans, mesas and beaches) that make
up landscapes.
¤ The hydrologic cycle: the contnual passage of water from reservoir to reservoir in the Earth
system.
F.2 Shaping the Earth’s surface
Uplift and subsidence; erosion and deposition
Uplift: relatve upward movement of a region
¤ Thickening of the crust
¤ Heatng of the lithosphere
¤ Rebound due to unloading
¤ Delaminaton (dense lithospheric mantle separates from the base of the plate and sinks)
Subsidence: relatve downward movement of a region
¤ Thinning of the crust due to stretching
¤ Cooling of the lithosphere
¤ Sinking due to loading
Topography: variaton in land-surface elevatons. Can be represented on a topographic map, or by
shaded-relief map, conveys the impression of three dimensions by shading appropriate slopes to
appear as if they are in shadows cast when the sun is low in the sky.
Digital elevaton map (DEM): a computer-produced portrayal of elevaton diferences commonly
using shading to simulate shadows; the data used to produce the map assigns elevatons to each
point on the map.
Relief: the elevaton diference between two points separated by a specifed horizontal distance on a
map. We can speak of a high-relief by big diferences and a low-relief by small diferences.
When relief develops various components to modify and shape the Earth kick in. Rock at the uplif or
just near it, weathers, fractures and weakens. On a slope this becomes a downslope movement: the
gravity-driven tumbling or sliding of debris from higher elevatons to lower ones. In additon this
causes erosion: the grinding away and removal of the Earth’s surface. And when moving fuids slow
down, depositon of the transported sediment takes place. Downslope movement, erosion, and
depositon redistribute rock and sediment, ultmately stripping it from higher areas and collectng it
in lower areas.
Rates of uplif and subsidence range between 0,01 and 10 mm per year. Erosion can carve out
several meters of substrate: the material just below the ground surface, in a single foodd storm or
landslide. The depositon of such an event can accumulate meters of debris.
