Geo 1001 - Paper Faults
This page contains a number of links to large GIF images that you can print,
cut, fold and tape to form paper models of different fault types. Use the
models to answer the questions below. At the bottom of the page there is
a link to the questions' answers, but don't use this link until you have
worked with the models to arrive at your own conclusions.
FAULT TYPE IDENTIFICATION
Different tectonic stresses will result in different types of fault movement.
So if you can identify what type of motion has occurred along a fault plane,
you can also identify what type of stress produced that motion. Geologists
study an area’s fault patterns to make interpretations of its present and
past tectonic history. To identify past fault motions, geologists have to
rely on the geometry of rock units that have been offset along the fault.
Identifying fault motion by this method takes some practice and it can be
difficult to visualize the three-dimensional nature of the rock units from
simple two-dimensional image.
IDENTIFYING FAULT MOTION – STEP BY STEP
- Determine whether you are looking at a map view (top of the block) or
a cross-section view (side view). This will be obvious with the models, but
may not be as obvious on a quiz illustration. On a quiz always make sure that
you know which view you are looking at before trying to identify the fault
- Determine the relative direction of motion along each fault. It is highly
recommend that you draw arrows on the models or quiz illustrations. It is
easy to confuse the blocks' relative motion if you just look at the image.
- Based on which view you are looking at, and the relative motion, determine
whether each fault is a normal, reverse, right-lateral or left-lateral fault.
Be sure to identify each fault separately, as the faults present in an area
could have formed at different times and from different tectonic stresses.
Faulted areas can have complex geological histories.
- Based on the fault type, determine which type of tectonic stress (tension,
compression or shear) created each fault.
MODELS 1 & 2
Models 1 and 2 both show a single fault that cuts a series of flat-lying
rock layers and a vertical igneous intrusion. For each model, try to determine
what type of fault motion occurred along the fault. Was it normal, reverse,
right-lateral or left-lateral motion? For each of the models, what type of
tectonic stress most likely created this fault?
MODELS 3 & 4
Models 3 and 4 both show a single fault that cuts a series of tilted rock
layers. Because the rock layers are tilted, there are two possible types of
fault motion that could create the geometry seen in each fault model. For
each model, try to determine which two types of fault motion might have been
responsible for the present pattern.
MODELS 5, 6, 7 & 8
Models 5, 6, 7 and 8 all show faults that cut a series of tilted rock layers
and an igneous intrusion. The addition of the intrusion should allow you to
identify a single type of fault motion that created this geometry. Was
the fault motion normal, reverse, right-lateral or left-lateral motion? For
each model, what type of tectonic stress created this fault?