What is the rule of V’s?
The rule of V’s in structural geology is an important methodology to understand the patterns formed by dipping geological contacts. This helps determine several geological factors regarding the area, including its steepness and the direction of water flow in that area.
However, before diving into the geology of the rule of V’s, let’s take a look at some of the complicated terminology used in the definition to make it easier for you to understand the concept.
Contour lines are lines on a map that visualize the steepness or depth of elevated land with equally spaced elevation points. Contour lines show the shape of the terrain and are helpful in understanding the topology of an area.
A geological contact is a border or boundary between two different types of rock bodies. These contacts can be the result of deposition, fault, or hot magma from Earth. Shifting plates can also be one of the causes of geological contact.
A strike is a line that forms when an inclined surface intersects with a horizontal bed. A striking line is used to determine faults, joints, or beds on the surface of Earth.
The dip is the angle between the horizontal surface and the inclining surface, such as geological contacts, and is perpendicular to the striking line.
Rule of V’s
Now that we’ve gone over all the essential terms one would need to understand the rule of V’s, here’s a simple definition of the rule:
The Rule of V’s is a graphical methodology of determining the direction of the dip that is caused by two geological contacts. This determination of dip angle and direction is done via observing the pattern made by the contacts as they cross a stream or valley.
The dipping contacts or units make a “V” shape where they intersect. The vertex of this V indicates the direction of dip between the two contacts.
The Rule of V’s is a great tool to determine the direction of dipping contacts and observe the contacts’ deflection. However, this rule and the V formed by the contacts should not be confused with contour lines as they act independently to the dipping of the contacts.
This rule does not always hold, but it is used as a general guiding principle which is helpful in most cases.
Why is the Rule of V’s important in geology?
So why exactly are we discussing Rule of V’s, and why is it so crucial in structural geology, topography, and mapping?
We know that we can use contour lines to depict and determine the topography elevation, or lack thereof. Contour lines help us indefinitely while trying to understand the topography of an area.
However, when contour lines are unavailable, or you can not make out the elevation of the contour lines, the rule of V’s comes in and saves the day. This V formed by the intersection of two contacts tells us the direction of the contact, where it originates from, and points in the upstream direction. This means that you can quickly figure out the direction of the flow of water running across this intersection of geological contacts by observing the point of the V.
This information can be beneficial when navigating new lands, rocky terrain, and exploring valleys and landmarks. The rule of V’s equips us with the sense of figuring out maps with ease. Rule of V’s has also allowed scientists and geologists to describe the geometry of strata and predict where the strata lie on the surface of Earth.