The value of missing time

Geological time that has gone missing

When you next look at sedimentary strata exposed in a hillside, cliff or road-cut, don’t just think of it as a pile of rock but as an expression of time; the length of time it took to deposit all that sediment.  The mountain exposure in the accompanying image is a great example.  Here, thousands of sedimentary layers, or strata accumulated one at a time, one upon the other.  Geologists tend to think of a succession like this as representing relatively continuous deposition of sediment, not necessarily uniform, but certainly continuous.  However, we also recognize that between each stratum there is probably some missing time that represents the amount of time taken to change from one set of environmental conditions to another.  For example, one layer may have been deposited as beach sand and the overlying layer in an estuary or tidal channel.  The length of time that is missing may be minutes, weeks, 100s or even 1000s of years that, from a geological perspective are like the blink of an eye. Continue reading →