Download Foam Faults

Foam Faults
A simple model of a dynamic process
Topics: Earthquakes,
Plate Tectonics, Faults
Materials List
 Blocks of stiff
packaging foam,
approx. 5 cm (2”)
thick
 Serrated knife (e.g.
bread knife) or
long-bladed scissors
 Permanent markers
This activity can be used
to teach:
Next Generation Science
Standards:
 Rock formations
(Grade 4, Earth and
Space Science, 1-1)
 Earth's features
(Grade 4, Earth and
Space Science, 2-2)
 Geosphere
(Grade 5, Earth and
Space Science, 2-1)
 Forecast catastrophic
events (Middle
School, Earth and
Space Science, 3-2)
 Geoscience Processes
(Earth and Space
Science,
Middle School, 2-2;
High School, 2-2)
 Cycling of Earth's
material
(Earth and Space
Science,
Middle School, 2-1;
High School, 2-1)
In this activity students will model the 3 main types of faults and examine the
terrestrial movement that occurs along the fault lines.
Assembly (Note: Adult implementation or supervision is required when foam is cut.)
1. Use permanent markers to draw a simple map of a small town with a river and/or
roads onto the top of the foam block.
2. Draw lines to represent at least 3 distinct layers around all sides of the block.
3. Cut the foam block into 2 pieces with the serrated knife or scissors. Make a
straight cut at an angle with respect to the tabletop (approximately 45°-60°), as
shown.
To Do and Notice
1. Place the foam pieces so the cut surfaces are back together.
2. Model normal fault movement by sliding the piece that is above the cut down the
other piece as shown below. Notice the relative positions of the horizontal lines
on each piece of foam.
3. Place the pieces back together again. Model thrust fault movement by sliding the
piece that is above the cut upwards relative to the other piece. Notice the
relationship of the horizontal lines in each block.
4. Turn the pieces around so that the angled edges face outward and put the pieces
together. Model strike-slip fault movement by sliding one piece horizontally
along the other. Notice the positions of the features drawn on top of the foam.
The Science Behind the Activity
The theory of plate tectonics is based on such evidence as the fit of certain continents,
the continent’s distribution of rock types, fossils, and ancient climatic zones plus the
locations of earthquakes, volcanoes, and the mid-oceanic ridges. Plate tectonics
provides a basis to explain how the Earth’s varied geologic terrain was formed.
Planet Earth is a layered planet with a dense, metallic core, a layer of hot liquid rock
(mantle), and a cold brittle surface (crust or lithosphere). The crust is broken up into
many huge pieces called plates. Convection currents in the liquid mantle pull a plate
into, away from, or along another plate (plate tectonics). Most earthquakes and
volcanoes occur near where 2 plates come together (plate boundaries). The forces
and pressures exerted as one plate moves under, along, or away from another plate
cause large cracks called faults to form at various locations near the plate boundary.
Ground movement along a fault causes an earthquake.
Developed and written by Eric Welker (RAFT) & Coral Clark (RAFT)
Copyright 2014, RAFT
There are three main fault types that occur on tectonic plates: normal, thrust, and strike-slip. A normal fault is one
in which the crust on one side of the fault line (fault plane) slides down the face of the crust on the other side of the
fault plane, exhibiting a vertical motion (refer to illustrations). At a thrust fault the crust that is above the fault
plane rises in relation to the crust below it (slides vertically up the plane). Thrust faults are sometimes referred to
as reverse faults depending on the angle the fault plane makes with respect to the crust surface. At strike-slip faults
the crusts on opposite sides of the fault plane move horizontally along the plane and away from each other.
Although most faults can be classified as one of the three types, many can exhibit behavior consistent with all of
them. A prime example of this is the San Andreas Fault, which runs through California. In Northern California,
the San Andreas behaves mostly as a strike-slip fault with the North American and Pacific plates sliding past each
other. Further south, the fault behaves more as a thrust fault because its path is not straight but instead has curves,
causing the two plates in those areas to press into each other. At other locations where the plates move away
(diverge) from each other the San Andreas Fault exhibits normal fault behavior. Mid-ocean ridges often exhibit
multi-type fault movement because as two tectonic plates diverge they cause stress on the oceanic bedrock resulting
in thousands of smaller faults that run perpendicular to the ridge.
Earthquake strength (magnitude) is measured using the Richter Scale, a logarithmic scale measuring the energy
released and ranges from 0 to 10 (strongest). How large the magnitude of an earthquake can be depends on several
factors including its depth from the surface, the displacement along the fault, the types of energy waves generated
in the ground, and properties of the crust at the fault plane. Because of these many factors, the damage caused by
earthquakes is not consistent for each fault type or location. The Mercalli Scale was developed to measure the
intensity (effect on the Earth’s surface) of an earthquake, including damage caused. It is a non-mathematical scale
that has 12 increasing intensity levels designated by Roman numerals (I to XII).
Taking it Further
 Identify common features for each fault type on a topographic map
 For other earthquake-related activities, see RAFT Idea Sheets Shake Table and Your Room in an Earthquake
Web Resources (Visit www.raft.net/raft-idea?isid=546 for more resources!)
 Excellent information on earthquakes is available from the USGS at: http://earthquake.usgs.gov/
 More information on the Mercalli Scale: http://earthquake.usgs.gov/learning/topics/mercalli.php
 Guidelines for earthquake preparedness: http://earthquake.usgs.gov/learning/faq.php?categoryID=14
Foam Faults, page 2
Copyright 2014, RAFT