To model the formation of an anticline.
the marker to make a line around the perimeter
of the sponge through the center of its
outside edge as shown in Figure 16.1.
the sponge with water to make it pliable,
then lay it on a table.
lifting the sponge, place your hands on
its short ends and push the ends toward
the center of the sponge. Observe the movement
and shape of the sponge.
Sum It Up!
The center of the sponge bends upward in an
The line drawn on the sponge divides the sponge
into layers representing
strata (layers of rock material) in the Earth's
crust. The force applied to
the sponge represents a form of stress, which
is a force that acts on rocks in the Earth's
crust, causing movement of a change in shape
or volume. The type of stress represented in
this experiment is compression (squeezing together)
of rock. Compression can cause rock to break
or bend. The movement of the sponge demonstrated
a folding, or bending of rock layers. A fold
producing an upward arch shape is called an