Faults
Faults are typically drawn as lines on geological cross-sections. They often form sharp boundaries, cutting off rock layers.
The crust of the earth is constantly subject to the push and pull of forces arising as continents are moved around. At the surface, where temperatures and pressures are lower, rock is brittle and tends to break when pressure is applied. Breaks in rock are known as fault or fracture lines. Once made, a fault line in the crust may persist for a long time, the brittle rocks on either side moving past each other in response to the forces they experience. Faults move sporadically in response to pressure build-up in the crust. Movement on fault lines causes rock surfaces to scrape against each other, creating vibrations in the crust which are felt as earthquakes.
When seen at surface, fault lines may mark sharp junctions between rocks of different ages or origins. Faults may also create surface features like mountain ranges or valleys as one side is pushed up or down. Hot material rising upwards from within the earth can cause the rocks in the upper crust to stretch apart in response, creating a faulted valley known as a graben.
When seen at surface, fault lines may mark sharp junctions between rocks of different ages or origins. Faults may also create surface features like mountain ranges or valleys as one side is pushed up or down. Hot material rising upwards from within the earth can cause the rocks in the upper crust to stretch apart in response, creating a faulted valley known as a graben.
Uplift creating a fault valley or graben
In the Jurassic, dolerite intrusion is often associated with faulting.
In the Cretaceous, faulting caused uplift of rocks that would ultimately form the mountain kunanyi/Wellington as well as an adjacent graben (the Derwent River valley) that would have hosted a lush, polar forest.
In the Tertiary many older faults were reactivated in response to pulling forces as Australia and Antarctic finally separated. Even today, crustal forces occasionally result in movement along an old fault line
In the Cretaceous, faulting caused uplift of rocks that would ultimately form the mountain kunanyi/Wellington as well as an adjacent graben (the Derwent River valley) that would have hosted a lush, polar forest.
In the Tertiary many older faults were reactivated in response to pulling forces as Australia and Antarctic finally separated. Even today, crustal forces occasionally result in movement along an old fault line
