|
Children's Ideas About Earth's Interior
Below are common ideas children in grades K-6 have about
this topic, compiled from research on children's ideas about science
(see the Session 1 Children's Ideas Bibliography).
Consider what evidence might refute this idea, and why a child
would be
likely to believe this?
1. Earth has a hot, molten
rock core.
|
|
Earth has a solid metal inner core, and a liquid metal
outer core. Temperatures in the inner core are near 6,000¾
C, while outer core temperatures are about 3500 ¾C. Children
have probably been exposed to popular media where “journeys
to the center of the Earth” portray dramatic rises
in temperature and molten rock. Hide
Response
|
2. Earth is mostly molten, aside from a thin crust.
|
|
Scientific knowledge of Earth's interior structure originates
in the information interpreted from seismic waves, which
behave differently as they pass through different materials
in the interior layers of the Earth. This data has revealed
that the Earth is made of four main layers: crust, mantle,
outer core, and inner core. Children's images of volcanoes
erupting red-hot lava may lead to their thinking that
the interior of the Earth consists of molten rock. This,
along with their experience being limited to Earth’s
surface, may cause them to reason that there are only
two layers. Hide
Response
|
3. Children often think the Earth’s crust is thicker
than it actually is, and are unaware of the correct proportions
of each of the Earth’s layers.
|
|
At its most thick, the crust is about 40km (25
miles) deep. This is a thin layer when compared to the
other layers of the Earth. The mantle is the thickest
layer at about 2,885 km (1,790 miles), followed by the
outer core at 2,270 km (1,400 miles), and then the inner
core, which has a diameter of about 1,216 km (755 miles).
Since children’s common experience is limited to
the Earth's crust, its size is often exaggerated in their
thinking. Hide
Response
|
4. There is a magnet at the Earth’s center.
|
|
Children have heard about the Earth’s magnetic
field and because of their experiences with magnets commonly
think that there is a giant magnet at Earth’s center,
and that this core causes Earth’s magnetic field.
The Earth does act like a giant bar magnet, with its “ends” being
the magnetic North and South poles. Both the inner and
outer core are made of metal — mostly iron — which
has magnetic properties. Current science theory suggests
that convection currents in the outer core may be responsible
for the Earth’s magnetic field. Hide
Response
|
5. Some children think there are hollow spaces inside
of the Earth, while others think that it uniformly solid.
|
|
Each of the Earth's layers, though different chemically
and physically, is continuous with no gaps or cavities.
Children's understanding of Earth's interior is not based
on any experiences they might have. Their perception
of the 'unseen' can resort to a simple, uniform model
of the Earth. Images of lakes, rivers, and caverns deep
inside of the Earth are perpetuated by popular fictional
media, which may account for the hollow Earth model held
by some children. Hide
Response
|
6. The mantle is a liquid or at
least partially liquid.
|
|
The Earth's mantle is actually quite complicated in
its structure. The upper mantle is solid at the top,
with a layer that is believed to be partly molten (liquid)
beneath it. The lower mantle is made up by solid rock
that is under conditions of extreme heat and pressure.
Children may have been taught about the physical state
of the layers of the Earth, including the mantle, and
this property of acting both like a liquid and a solid
is likely to be confusing. Hide
Response
|
Bibliography:
Baxter, J. Learning Science in the Schools: Research Reforming
Practice, edited by In Duit and Glynn. Mahwah, NJ: Lawrence Erlbaum
Associates: 1999.
Lillo, J. “An Analysis of the Annotated Drawings
of the Internal Structure of the Earth Made by Students Ages
10 to 15 From Primary
and Secondary Schools in Spain.” Teaching Earth Sciences 19,
no. 3 (1994): 83 – 87.
Sharpe, J., Mackintoch, M., and Seedhouse,
P. “Some Comments
on Children’s Ideas About Earth Structure, Volcanoes, Earthquakes,
and Plates. ” Teaching
Earth Sciences 20, no. 1 (1995): 28 – 30.
|
prev:
mapping earth's interior
