# folds

## monocline

A monocline is a simple bend in the rock layers so that they are no longer horizontal (see Figure 1.1 for an example). At Utahs Cockscomb, the rocks plunge downward in a monocline. What you see in the image appears to be a monocline. Are you certain it is a monocline? What else might it be? What would you have to do to figure it out?

## folds

Rocks deforming plastically under compressive stresses crumple into folds. They do not return to their original shape. If the rocks experience more stress, they may undergo more folding or even fracture. You can see three types of folds.

## syncline

A syncline is a fold that bends downward. The youngest rocks are at the center and the oldest are at the outside (Figure 1.3). When rocks bend downward in a circular structure, that structure is called a basin (Figure 1.4). If the rocks are exposed at the surface, where are the oldest rocks located? Click image to the left or use the URL below. URL: Anticlines are formations that have folded rocks upward. (a) Schematic of a syncline. (b) This syncline is in Rainbow Basin, California. Some folding can be fairly complicated. What do you see in the photo above?

## anticline

Anticline: An anticline is a fold that arches upward. The rocks dip away from the center of the fold (Figure 1.2). The oldest rocks are at the center of an anticline and the youngest are draped over them. When rocks arch upward to form a circular structure, that structure is called a dome. If the top of the dome is sliced off, where are the oldest rocks located?

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

rocks that deform plastically under compressive stresses crumple into this.

``````a) plateaus

b) calderas

-->  c) folds

d) valleys
``````

this type of stress creates folds.

``````a) tension

b) shearing

-->  c) compression

d) no stress
``````

an anticline in three dimensions is a basin.

``````a) true

-->  b) false
``````

a monocline

``````a) is a tilted rock layer that is no longer horizontal.

b) could be the limb of a syncline.

c) could be the limb of an anticline.

-->  d) all of the above
``````

a dome is a structure made when rocks arch upward.

``````-->  a) true

b) false
``````

if a dome is eroded away, what are the ages of the rocks from inside to outside.

``````a) youngest in the inside; oldest in the outside.

-->  b) oldest in the inside; youngest in the outside.

c) rocks are the same age through the dome.

d) random. some old rocks are inside and some are outside.
``````

an anticline has rocks that bend.

``````a) downward

b) diagonally

c) vertically

-->  d) upward
``````

the michigan basin is made by rock bending

``````-->  a) downward

b) diagonally

c) vertically

d) upward
``````

when rocks are bent into a fold, they may go back to their original shape if the stress is released.

``````a) true

-->  b) false
``````

in a syncline, the youngest rocks are outside and the oldest rocks are in the center.

``````a) true

-->  b) false
``````

## diagram questions

No diagram questions associated with this lesson