Geoscience Reference
In-Depth Information
In sedimentary basins, successful estimates of vertical movements have been
made using the thicknesses of sediment layers accumulating over different time inter-
vals in different depths of water. In areas of mountain building, amounts of vertical
uplift have been estimated using certain indicator minerals that show the rates of cool-
ing that rocks have experienced as they were brought up to the surface. However, both
these approaches are only really possible in areas that have been subjected to move-
ments of the Earth's crust that are large and continuous enough to completely dominate
other possible sources of error.
Local horizontal movements are also difficult to estimate, although fold and/or
fault patterns may allow a simple measure in some cases. Movement of sediment
across the Earth's surface by rivers or sea currents can be estimated if mineral grains
in the sediment can be tracked back to the areas from which they have come. In the
detailed consideration of landscapes in this topic, we have to rely on using the widest
possible range of types of evidence, carefully distinguishing the times and scales in-
volved. Even then, we are often left with probable movement suggestions rather than
certainties.
