Convection currents describe the rising, spreading, and sinking of gas, liquid, or molten material caused by heat application. Convection can also be described as a physical process that transfers heat.
Convection currents under the plates move the continental plates in different directions. The heat source that drives convection currents is radioactivity deep in the Earth's mantle. Here, the dense (lighter) continental material rises, and the denser (heavier) continental material sinks. The convection currents of tectonic plates depend on changes in temperature and density. The density of the material depends on the temperature. When a matter is heated, it expands and becomes less dense. As matter cools, it contracts and becomes denser.
Figure 1: An extract from Drivers Of Plate Tectonics simulation by Labster.
Now imagine boiling a pot of water on the stove. When the water at the bottom of the vessel is heated, its volume expands, which reduces its density and it rises to the surface of the pot. There the water cools and shrinks in volume, its density increases again, and gravity forces it to sink to the bottom of the pot. The hot and cold water kept alternating as they rose and fell. A cycle of material movement is created between the surface and the bottom of the boiling pot. This cycle is called a convection current.
Figure 2: Using boiling water to explain Convection currents
Read on to find out why this can be a difficult topic for teachers and students, five tips to help change that, and ideas for why virtual labs can make things easier.
There are three reasons in particular why drivers of plate tectonics can be difficult, even for the most diligent of students.
Earth's convection currents, which drive plate tectonics, originate beneath the Earth's crust, particularly in the mantle; you can't see or feel it. Not being able to visualize the process and see how it applies to the real world can frustrate learning and make it difficult for students to stay motivated.
The Earth's interior can be divided into three layers of main composition: core, mantle, and crust, which differ in their chemical properties.
Figure 3: Earth's layers are defined by chemical properties (core, mantle, and crust) and physical properties (inner and outer core, lower mantle, asthenosphere, and lithosphere)
Core: The core is the deepest layer of the earth and consists of metals such as iron (Fe) and nickel (Ni). It can be divided into an inner core and an outer core based on its mechanical behavior. The inner core is solid despite experiencing the highest temperatures on Earth. Great pressure from the top layer of the earth prevents it from melting. The outer core is a liquid layer. Convection currents in the outer core create the earth's magnetic field.
Mantle: The mantle is the largest layer on Earth by volume and is located between the crust and the core. The mantle is mostly composed of silicates (silica and oxygen-containing minerals). Jacket material behaves differently depending on its depth. The lower mantle is less elastic than the asthenosphere above because of the higher pressure. Although the lower mantle is dense, it deforms and flows in convection currents for long periods. The asthenosphere is also dense but mostly behaves like a viscous liquid. This allows the existence of convection currents that drive the movement of tectonic plates.
Crust: The cortex is the outermost and thinnest composite layer. There is the oceanic crust and continental crust. The oceanic crust is the denser of the two and lies beneath the oceans. It consists mostly of basalt rock with high magnesium (Mg) and iron (Fe) levels. The continental crust is composed of less dense rocks that are similar in composition to granite and make up nearly all of the Earth's surface. The crust and upper mantle together make up the lithosphere. This layer is cold and brittle, and breaks up into many pieces that we call tectonic plates
Tectonic plates move about 2 to 3 cm yearly, and convection currents drive this movement. Although the mantle is mostly solid, it moves like a viscous liquid or flexible plastic.
Figure 4: Convection currents and the movement of tectonic plates. A - A lump of warmer, less dense mantle. B - Magma reaches the surface and forms a new crust. C - Convection currents cause tectonic plates to move. D - The cooler, denser plate is subducting. E - The sheath material cools and sinks.
Earth's core and mantle generate heat through radioactive decay. As the mantle warms, its density decreases, causing it to rise (Fig. 1- A) until it reaches the asthenosphere slowly. Since it could not pass through the upper crust, it was pushed aside. The movement of the asthenosphere flowing against the lithosphere causes friction and plate motion (Fig. 1 - C). During lateral movement, the mantle material cools again, becomes denser, and sinks toward the lower mantle (Fig. 1 - E). This process repeats itself in a continuous cycle.
The forces caused by convection in the mantle can split the lithosphere (Fig. 1 - B), allowing magma to rise (divergent plate boundaries). As it cools, it forms a new oceanic crust. Because the ridge is the highest part of the plate, a gravitational force causes the plate to move away from the ridge. This force is called thrust. Plate tug is another process that contributes to the movement of tectonic plates (Fig. 1 - D), with denser, colder plates subducting under less dense plates (converging boundaries). Concave plates pull abandoned plates into the sink like a tablecloth, pulling cutlery off the table.
With these points in mind, here are five things you can include in your Driver's of Plate Tectonics class today to make it more engaging, accessible, and enjoyable for you and your students.
To make the lesson "Driver's of Plate Tectonics: Replicate Earth's convection currents" more motivating, it is important to look back at the history of Earth's convection currents. Arthur Holmes discovered convection currents in 1930. He showed that convection currents in the mantle played a key role in continental drift.
Arthur Holmes proposed a theory that states that convection current occurrence in the Earth's mantle is responsible for pushing and pulling continental plates.
This movement of tectonic plates is caused by convection currents in molten rock in the mantle beneath the crust. Earthquakes and volcanoes are short-term consequences of these tectonic movements.
Figure 5: A snippet from Drivers Of Plate Tectonics simulation by Labster.
Evidence of terrestrial convection currents driving plate tectonics can be observed on Earth.
Hawaiian Lava Stream On Mount Kilauea
Sea Floor Deployment
Mnemonics can be a huge help in understanding complex topics like drivers of Plate tectonics. There are a few ways to get around it using memory aids such as "Core Man Crush" which can be used to represent the three layers of Earth's interior namely:
Core - Core
Man - Mantle
Crush - Crust
A unique way to teach drivers of plate tectonics is through a virtual laboratory simulation. At Labster, we’re dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems, inside an immersive and engaging 3D universe.
Check out the Labster driver's of plate tectonics simulation that allows students to learn about cellular respiration through active, inquiry-based learning. In the simulation, students will go on a mission to learn about the Earth’s internal processes and mechanisms that drive the movement of tectonic plates.
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