(Earth Science for ages 5+)
Earthquakes happen every day all over the world. Most of the time, they are very mellow and unnoticeable to the people living nearby, but sometimes, they are very strong and can even destroy buildings and streets.
But if we only notice the big quakes, how do we know smaller quakes are happening at all? To measure these movements within the Earth’s surface, scientists use a tool called a seismograph, which measures the seismic activity, or vibrations created when tectonic plates shift and bump into each other.
By watching the video above, you can learn how to build your very own seismograph at home to better understand how this technology works. Here’s what you’ll need:
Paper or plastic cup
Scissors or boxcutter
Hole punch (optional but helpful)
Coins, nuts, rocks, or other objects for weights
Adult supervision (Adult supervision at all times please)
- Start by cutting off the flaps of the cardboard box using the scissors or boxcutter. This task may be better suited for an adult, but either way, be very careful so as not to cut yourself.
- Next, set the box up on one of its short sides. This will be the bottom of your seismograph. In the middle of the top side, poke 2 small holes about 10 centimeters apart to be used for hanging the cup.
- Using the hole punch or scissors, punch 2 small holes on opposite sides of the cup near the rim. Using the scissors, poke a hole through the middle of the bottom of the cup. This is where your marker will be inserted into the cup, so make sure the hole is big enough to hold the marker.
- You can hang the cup inside the box using 2 pieces of string that are equal in length by tying one end through one of the holes in the cup, and the other through one of the holes in the top of the box. You could also use one long piece of string by tying one end to one of holes in the cup, then feeding the string up through one of the holes in the top of the box, down through the other box hole, and finally tying the other end of the string to the other hole in the cup. Your cup should be suspended in the box and not quite touching the bottom.
- Next, take the lid off of your marker and push it through the hole in the bottom of the cup. The tip of your marker should be just touching the bottom of the box.
- Add your coins, rocks, or whatever else you have handy to weigh down the cup. Adjust the marker if needed so that it is just barely touching the bottom of the box again.
- Cut a sheet of paper into four equal strips and then tape them together end-to-end to create a long, narrow strip of paper.
- Cut slots into the bottom of the sides of the box using the scissors or boxcutter. Slide the strip of paper through both slots, and your seismograph is ready to detect quakes!
- Shake the box while pulling the paper through the slots at a steady pace. This might be easier done with two people: one to shake the box and the other to pull the paper through. What do you notice when you shake the box really hard and fast? What about gentle shakes?
An official seismograph is a lot more sophisticated than the one you just built, but it works in a similar manner. When faults within the Earth’s crust slip or when magma splits through the crust, seismic waves ripple through the Earth, much like dropping a pebble into water and seeing the ripples radiate outward.
An official seismograph is probably a little smaller than the one you made, with the average one being 5.5 inches wide by 6.5 inches high by 11.5 inches long (about the size of a small shoebox). It works by using a weight (your weighted cup) attached to a pen (your marker) that marks a revolving role of paper (your paper strip).
The weight is attached to a spring (your string) and bolted to the ground so when an earthquake occurs (you shaking your box), the weight will move in response and the pen will draw the ripple.
The resulting graph that is drawn on the paper is called a seismogram and geologists (scientists who study the Earth) can look at these graphs to keep track of movements within the Earth’s crust and to measure the strength of the seismic forces.