Lake Afton Public Observatory, Copyright ~ 1995. All Rights Reserved (permission to copy for educational use is granted)

Making a Crater
Notes for the Teacher

Objective:

This exercise is designed to show the student how craters are formed nd how some of the characteristic features of a crater are produced.

Materials Needed:

cigar box (or similar box or pan), flour, paprika or cinnamon powder, magnet, steel marbles or ball bearings, small pebbles, pellets or BB's.

Suggestions:

1. This activity is designed for one student or a pair of students.

2. Be sure to place some newspaper or cloth below the box to catch the excess debris. This lab can get a little messy if not properly supervised.

3. Some background information should include: craters; meteors; features on the Moon (maria, highlands, craters, perhaps the Apollo missions).

4. There is one feature of a crater that can't be reproduced in this exercise the central peak of some larger craters. This is caused by the heated, molten material from the impact splashing up and hardening before it has a chance to settle in the bottom of the crater. Lake Afton Public Observatory can suggest some films and/or videos illustrating this phenomena.


MAKING A CRATER

We all know that the moon has craters. But, did you ever stop to think how those craters were formed or that there are craters right here on Earth. In fact, you will be making your own craters in much the same fashion as real craters are formed (except your craters will be very small compared to the ones you can see on the moon). The Moon, the Earth, and everything else in the solar system is being hit by debris from space all the time. Most of this material is very small compared to the asteroid- sized objects that hit the Earth and Moon billions of years ago. Most of the material which hits Earth burns up in the atmosphere before it ever reaches the ground. However, once in a while a piece of this outer space material makes it all the way to the ground and forms a crater. Meteor Crater in northern Arizona is a good example of an impact crater.

The Moon however, is literally covered with craters. Why isn't Earth? Most of the craters on Earth and the Moon were made billions of years ago. Since that time water and wind on Earth has eroded the craters. Only those craters that were formed a few thousand years ago can be seen today. The Moon however, doesn't have an atmosphere and therefore no wind or water. So, the craters from billions of years ago have remained essentially undisturbed and the Moon looks the same today as it did millions of years ago.


You will be making your own craters and investigating the same type of features that astronomers look for in a real crater. Some of these features are:

1. Crater size and how it compares to the size of the meteor.

2. The rim of the crater. It's depth, shape, clarity, etc.

3. The rays of a crater. What causes rays and how large they are?

4. Crater location and how this is used to determine age.

5. Crater size and how this is used to determine age.


PROCEDURE
1. Take the cigar box or pan and fill it with flour to a depth of about an inch. Then gently shake or tap the pan until the flour is smooth.

2. Sprinkle the paprika on top until the flour is barely covered. This represents the Moon's layers with its lighter material beneath a thin layer of darker volcanic remains.

3. Drop the large (about 1/4 inch diameter) steel ball in the middle of the box. Then very carefully remove the ball with a magnet.

4. Now take a few of the small objects (pellets, BB's, etc) and drop them into the box from straight overhead. Drop each one from a different height.

5. Next, take a few of the small objects and throw them very carefully into the box at an angle.


Name__________________________________________________ Date____________________

MAKING A CRATER
OBSERVATIONS & QUESTIONS

1. Compare the size of the large crater to the size of the steel ball. Are they the same?

2. Compare the size of all the craters to the size of the objects that formed them. Do you see any differences between any of the craters?

3. Describe the shape of the rims of:

a) the large crater.

b) a small crater.

c) one of the craters formed when you threw the pellet at an angle.

4. Which of the craters has the sharpest, most well defined rim? 5.Which of the craters has the tallest rim?

5. Describe any rays you see coming from the craters.

6. Describe how craters are formed on the Moon and planets.

7. Why are there relatively few craters on the surface of the Earth?


(Teacher's Edition)

MAKING A CRATER

OBSERVATIONS & QUESTIONS

1. Compare the size of the large crater to the size of the steel ball. Are they the same?

No, the crater is larger in diameter than the steel ball. The material is forced away from the ball on impact.

2. Compare the size of all the craters to the size of the objects that formed them. Do you see any differences between any of the craters?

In general, the size of the crater is larger than the object. The smaller the object, the less is the difference in size from object to crater. The objects that strike the surface at an angle produce longer, more oval craters.

3. Describe the shape of the rims of:

a) the large crater.

The rim is very sharp (i.e. well defined), somewhat raised above the surface, with rays of the lighter material underneath spread out over the darker material on the surface.

b) a small crater.

The rim is sharp and closer to the size of the object. It may have a few rays radiating outwards, but not as many as the large crater.

c) one of the craters formed when you threw the pellet at an angle.

The rim will be more "piled up" on one side, it will be sharp on this side and have a more "scooped out" appearance on the side that it came in on. More than most likely, any rays will only be on the side opposite the "scooped out", incoming side.

4. Which of the craters has the sharpest, most well defined rim?

Either one thrown with a high velocity or the large one.

5. Describe any rays you see coming from the craters.

There will be streaks of lighter colored material dusted over the darker material in a roughly "spoke" pattern. (i.e. going outwards from the crater in streaks)

6. Describe how craters are formed on the Moon and planets.

When an object from space encounters another object, the collision will result in a crater being formed. The "space" object slams into the other object and violently deforms and heats it up. It is, very much, like a rock thrown into a pond. A hole is made in the pond by the rock and splashes water around the "hole". Except the hole does not entirely smooth out like water, but solidifies and records an impact crater.

7. Why are there relatively few craters on the surface of the Earth?

Because wind and water erode away the evidence of an impact crater here on Earth.