Essential Science for Teachers: Earth and Space Science
Journey to the Earth’s Interior Children’s Ideas About Earth’s Interior
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.
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.
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.
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.
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.
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.
- 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.
Session 1 Earth’s Solid Membrane: Soil
How does soil appear on a newly born, barren volcanic island? In this session, participants explore how soil is formed, its role in certain Earth processes, its composition and structure, and its place in the structure of the Earth.
Session 2 Every Rock Tells A Story
How can we use rocks to understand events in the Earth's past? In this session, participants explore the processes that form sedimentary rocks, learn how fossils are preserved, and are introduced to the theory of plate tectonics.
Session 3 Journey to the Earth’s Interior
How do we know what the interior of the Earth is like if we've never been there? In this session, participants examine the internal structure of the Earth and learn how it is possible for entire continents to move across its surface.
Session 4 The Engine That Drives the Earth
What drives the movement of tectonic plates? In this session, participants learn how plates interact at plate margins, how volcanoes work, and the story of Hawaii's formation.
Session 5 When Continents Collide
How is it possible that marine fossils are found on Mount Everest, the world's highest continental mountain? In this session, participants learn what happens when continents collide and how this process shapes the surface of the Earth.
Session 6 Restless Landscapes
If almost all mountains are formed the same way, why do they look so different? In this session, participants learn about the forces continually at work on the surface of the Earth that sculpt the ever-changing landscape.
Session 7 Our Nearest Neighbor: The Moon
Why is the Moon, our nearest neighbor in the solar system, so different from the Earth? In this session, participants explore the complex connections between the Earth and Moon, the origin of the Moon, and the roles played by gravity and collisions in the Earth-Moon system.
Session 8 Order out of Chaos: Our Solar System
Why do all the planets orbit the Sun in the same direction and why are the planets closest to the Sun so different from the gas giants farther out? In this session, participants gain a better understanding of the nature of the solar system by examining its formation.