Relative dating exercise geology
Thus, we can deduce that the mudstone and shale are older than the rhyolite dike.
But, since the rhyolite dike does not cut across the shale, we know the shale is younger than the rhyolite dike.
Thus, we know that the dike is younger than the mudstone, sandstone, and shale.
Similarly, the rhyolite dike cuts only the mudstone and the sandstone, but does not cut across the shale.
where the same features that could be seen forming in modern environments.He concluded that process that are currently operating on the Earth must be the same processes that operated in the past.This principle is often stated as "the present is the key to the past".From the beginning of this course, we have stated that the Earth is about 4.6 billion years old.How do we know this and how do we know the ages of other events in Earth history?Once these age relations were worked out, another principle fell into place - the principle of fossil succession.