Evidence about Past Earthquakes From Faults By: Thomas Solowynsky, Tom Mulally, Victoria Flis, Omar Oregel

Faults  There are many faults that tell us different effects and are caused by earthquakes.  Faults form because of extension or compression.  In Moab, faults are not active right now.  We will explain about earthquakes and what is different between small faults and huge faults.

Extension makes normal faults  Stretching of the ground is called Extension  Extension causes normal faults to form

Identify Faults  Some layers and faults are exposed so clearly like show different kind of stones and slips. Its can tell us if its compression or extension. Or some layers and faults are in a mess and many slips. Sometime its hard to identify the stone because it was mixed up and deformation.

Earthquake  Earthquakes tend to start from the movement in aethenosphere and it will hit to lithosphere.  In the western of U.S., earthquakes can go up to magnitude 6.0 or 7.0.

Small Faults  Small faults were caused by either many small or one medium earthquakes.  In Moab and Arches National Park, small faults tend to clearly show slips and layers.  It is easy to identify kind of rocks and match the layers.

Examples of small faults Small Faults

Slip on small faults Slip on faults

Huge Faults  Earthquakes cause the rocks to move by slip on the fault.  Near the fault, the rock gets broken into lots of pieces from power of earthquakes.  Lots of power = lots of broken rocks  There is a lot of grinding close to faults.

Huge Faults Fault Very Broken Rocks! Not Very Broken Rocks Slip

More About Huge Faults  Water goes through faults easily because of cracks and broken rocks.  When old age rocks are together with younger age rocks, we must have a big fault.  Over time rain falls onto the mountain and the mountain is made more smooth shaped. This is erosion.

Huge Fault Features Different color Fault Youngest Rocks Young Rocks Oldest Rocks

Conclusions  Evidence in the field tells us that old faults once produced earthquakes Small earthquakes  Simple cracks with small amount of slip Large earthquakes  Lots of broken rocks  Large faults are easy places for water to flow

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