Density / Structure of the Earth Webquest
Station 1
Evidence: A marshmallow peep was placed into the microwave, then the microwave was
turned on to high. The photographic evidence of what happened is below.
1. What has happened to the mass of the marshmallow peep?
2. What has happened to the volume of the marshmallow peep?
3. What has happened to the density of the marshmallow peep?
Station 2
When you observe rocks in a stream or river, you often find they share common
characteristics. The fast moving water moves rocks downstream. As the water slows down, the
rocks slowly stop moving. Typically the largest rocks stop moving first while the smaller sized
rocks continue moving until the water slows down even more.
Below are pictures of six different-sized particles, made of the same type of rock.
4. Which particles will fall to the bottom of a fast-moving stream first?
5. Which particles will be carried downstream the greatest distance?
Imagine that all of these particles fall from a river into Bear Lake.
6. Which particle will hit the lake bed (the bottom of the lake) first?
7. Where will most of the tiny grains be deposited?
Station 3
Have you ever walked along a beach and wondered
why parts of it were sandy and other parts were
rocky? When the waves hit the beach, the sand and
rocks carried in the water fall out. The denser rock
particles are dropped first along the shore, while
the less dense sand particles are carried further up
the beach.
8. Which are the most dense particles in this jar
filled with sediment from the beach?
9. If you want to walk barefoot along the beach, should you walk right at the water’s edge?
Explain.
Station 4
Use the on-screen calculator to determine the density of each of these substances.
S ubstance
M ass in grams
Volume in cubic
centimeters
10. Gold
193.2g
10 cm3
11. Oxygen
1.33g
100 cm3
12. Water
10.0g
10 cm3
13. Helium
1.663g
10,000 cm3
14. Mercury
67.75g
5 cm3
15. Copper
224g
25 cm3
Density in
grams/cubic
centimeters
16. Which substance would hit the bottom of a jar first?
Station 5 What’s at the bottom of a stream or river can tell us a lot about how fast the water
moves in the river.
Slow moving rivers like the Mississippi
are relatively flat, and the bottom of the
river is covered with mud (silt) and sand.
There are very few rocks because the
water does not have enough energy to
carry them along, and they soon get
covered with sand and silt.
Fast moving rivers have enough energy
to carry small rocks downstream, and
keep the sand and silt suspended
(mixed) in the water as it flows
downhill.
The bottoms of steep, fast-moving
rivers are covered with rocks, not sand.
This biker is riding through a wash,
where a stream once flowed.
17. Was this stream fast-flowing, slowflowing, or somewhere in between?
18. What evidence helps you decide?
Station 6
Raised relief globe
Flat surface globe
19. What differences
seen when the two types
of globes above are
compared?
20. How is the raised
relief globe a more
accurate model than the
flat surface globe?
Look close-up photograph of the raised relief globe below. 21. Why is this not a good model?
Possible model problems:
Each globe is an attempt to show the placement and size of
continents in relationship to the entire Earth. When you
look closely at the raised relief globe, you see an attempt to
demonstrate differences in elevation. Mountains are shown
as being raised well above the Earth's surface. While it is
true that mountains are higher than the average surface of
the Earth, the scale does not match the globe. At the scale
of a globe, the entire surface would appear flat. At this
scale, when compared with the enormous size of the entire
earth, even Mt. Everest would appear flat!
Maps as models:
When you look at a map, you observe relationships
between parts of the Earth. Many maps are designed
to allow you to place them on a wall. These large
maps are very convenient models to use when
observing the entire Earth at the same time. The
major problem with maps as a model is that it distorts
objects.
Remember that the Earth is really round. When you flatten it out into a map form, it stretches
out the poles and these areas appear larger than they really are. In the flat map above,
Greenland appears to be about the same size as North America. It is, however, actually much
smaller!
22. Why is a flat map not a good model of the earth?
Station 7
If someone told you to figure out what in inside earth, what would you do? How could you
use evidence to figure out what is inside our planet? How did scientists figure it out?
Geologists study earthquake waves to “see” Earth’s interior. Waves of energy radiate out
from an earthquake’s focus. These waves are called seismic waves. Seismic waves go
different speeds through different materials. They change speed when they go from one type
of material to another. This causes them to bend. Some seismic waves do not travel through
liquids or gases. They just stop. Scientists use information from seismic waves to understand
what makes up the Earth’s interior.
Scientists also study meteorites to
learn about Earth’s interior.
Meteorites formed in the early solar
system. These objects represent
early solar system materials. Some
meteorites are made of iron and
nickel. They are thought to be very
similar to Earth’s core. An iron
meteorite is the closest thing to a
sample of the core that scientists can
hold in their hands. Earth has a
magnetic field, so there must be
metal within the planet. Iron and
nickel are both magnetic and very dense, so we think they are the main components of the
core. We know that the mantle is made of molten rock because of lava that oozes out of
volcanoes.
In addition, scientists have calculated the overall mass and volume of the earth, and thus the
density of the whole earth. The density of the whole earth is higher than the average density
of the materials in the crust, so the inside of the earth must be more dense than the crust.
23. Give one piece of evidence from the information above that explains how we know that
the outer core of the Earth is a liquid.
24. Give one piece of evidence from the information above that explains how we know that
the density of the inner core is more dense than other layers of the earth.
25. Give one piece of evidence from the information above that explains how we know that
the mantle is plastic, molten rock.