Table of Contents
What can cause older rock layers to be found above younger rocks?
However, the most common mechanism to produce older rocks on top of younger is by thrust faulting. Thrust faults form where rocks are being compressed, usually by plate tectonic mechanisms. Thrust faults rip up older strata and pile it on top of younger rocks.
Which principle tells us younger rocks must be above older rocks?
law of superposition, a major principle of stratigraphy stating that within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence.
What is working out whether rocks are younger or older called?
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence. The method of reading the order is called stratigraphy (layers of rock are called strata).
How is the law of superposition used?
The law of superposition states that each rock layer is older than the one above it. So, the relative age of the rock or fossil in the rock or fossil in the rock is older if it is farther down in the rock layers. Relative dating can be used only when the rock layers have been preserved in their original sequence.
How is the relative age of a rock determined?
The relative age of a rock is its age in comparison with other rocks. If you know the relative ages of two rock layers, you know which is older and which is younger, but you do not know how old the layers are in years. In some cases, it is very tricky to determine the sequence of events that leads to a certain formation.
How do you know how old rocks are?
Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale.
Which is younger a fault or a rock?
The fault is younger than the rocks above it. The fault is younger than the rocks it cuts through. The fault is older than the rocks above it. The fault is older than the rocks it cuts through. Q. Analyze the seashell found in the white layer.
Which is the youngest layer of sedimentary rock?
The intrusion (D) cuts through the three sedimentary rock layers, so it must be younger than those layers. The principle of superposition states that the oldest sedimentary rock units are at the bottom, and the youngest are at the top. Based on this, layer C is oldest, followed by B and A.