Most people think of the rugged, soaring heights of the Himalayas, Andes, and Alps when they think of mountains. But some of the Earth's smaller mountain ranges were once soaring peaks, too. The Appalachian Mountains started forming 480 million years ago when the North American and Eurasian continental plates collided. The Appalachians were once taller than the Himalayas. The range stretches from Newfoundland in southeastern Canada down through the eastern United States to central Alabama. However, erosion has taken its toll on the Appalachians. Today, some of its higher peaks are less than a third of the height of Everest.
As you reach GZ you will notice the mountain chain slightly to your right. This chain is part of the Appalachian Mountains. You will also notice how this mountain chain tapers off into the valley and plains which you are standing in. Here you will find a unique feature that has been uncovered due to erosion. After observing this unique earth cache feature, you will need to answer a few questions regarding this site as well as use the useful information on the cache page to determine if this is a fault or a fold .
When determining what a fault or a fold is, a way of measuring them, forces that cause them, and the different types, would be defined as follows:
Folding – the bending of rocks in the Earth as a result of compressional tectonic forces such as continental collisions. Occurs at depth in the Earth.
Faulting – fracturing of rocks in the Earth causing breakage and slip parallel to the fracture. Caused by compressional, extensional and shear forces. Occurs close to surface of the Earth.
Geological measurements in the field
Strike – direction of intersection of a rock layer with a horizontal surface.
Dip – measured at right angles to the strike is amount of tilting. i.e. angle that the bed inclines from the horizontal.
Forces that cause deformation
Compressional – forces that squeeze rocks together and cause shortening.
Tensional – forces that stretch and tend to pull a body apart, extensional.
Shearing – forces that push two sides of an object in opposite directions.
Types of folds
Anticline– upfolds or arches of folded, layered rocks.
Syncline – downfolds or troughs of folded, layered rocks.
Limbs – The two sides of a fold.
Axial plane – imaginary surface that divides a fold as symmetrically as possible, with one limb on either side of the plane.
Fold axis – line made by the lengthwise interaction of the axial plane with the beds of the fold.
Plunging fold – a fold whose fold axis is not horizontal, but dips at some angle.
Asymmetrical fold – fold that has one limb dipping more steeply than the other. Caused by increased horizontal forces.
Overturned fold – fold that has been subjected to intense deformation and has one limb that has been tilted beyond the vertical.
Faults
Fault plane – the surface along which a rock formation fractures and slips.
Dip-slip fault – relative movement up or down the fault plane.
Normal fault – dip slip fault where the rocks below the fault plane move upwards – caused by extensional forces.
Reverse fault – dip slip fault whare the rocks below the fault plane move downwards – caused by compressional forces.
Strike-slip fault – fault whose movement is horizontal, parallel to the strike of the fault plane – caused by shearing. Right lateral fault – strike slip with movement to the right, Left lateral fault, strike slip fault with movement to the left.
Oblique-slip fault – fault where move is simultaneously along strike and either up or down – movement at an angle along the fault plane.
Thrust fault – very low angle reverse fault where one formation is thrust over another – process called overthrusting.
Rift valley – depression in the Earth caused by extensional forces causing normal faults that allow a large block of the Earth to drop. Creates a long narrow trough in the Earth bounded by fault planes – East African rift valley, Rio Grande Rift.
To see how this Earth Cache was made, click on the following link and follow the instructions
http://wc.pima.edu/~bfiero/tucsonecology/setting/geology_faults.htm
Educational requirements:
To claim a find for this earthcache please email via my profile link and the answers to the following questions. Please include "Fault or Fold It" in the heading of your message to avoid confusion. "Found" logs without this information will be deleted.
1. In your opinion, is this geological feature a fault or a fold?
2. If this geological feature is a fault, what type is it and how did it form? If this feature is a fold, what type is it and how did it form?
3. When observing this feature at ground zero, how wide would you determine it to be and how many inches thick is the rock layer that flows from one end to the other?
4. In your opinion, what type of force was used to make this geological feature?
5. Although it is not a requirement, a picture of you close to or at GZ would be a perfect way of remembering how you spend a few minutes of your time checking out this Earth Cache!