WGU C451/GNC2/1NC1 Integrated
Natural Sciences Module 6
Define convection current. – ✔✔Circular currents in the mantle caused by the magma being
heated by the core off the Earth.
Explain how convection cells cause local winds – ✔✔Local winds are the result of convection on
a small scale. They occur when Earth’s surface is heated unevenly. For example, you’ve probably
noticed that large bodies of water, such as lakes and oceans, are often much cooler than the
nearby land surfaces during the day. The air above the warm surface absorbs heat from the
surface and warms up. The warm air rises up. As it rises, it cools and begins to sink again. This
forms a convection cell, as we saw earlier. Rising air creates a region of low pressure near the
warm surface, and sinking air creates a region of high pressure near the cold surface. Air
naturally moves from high pressure toward low pressure. This movement is wind. This is why
you will often feel a cool breeze blowing from a body of water, such as a lake or ocean, onto the
land on a warm day.
Explain how convection cells cause Hadley Cells – ✔✔Convection also plays a role in
distributing heat throughout the atmosphere. The very large-scale convection cells in the
atmosphere are called Hadley cells. They result from differences in the amount of sunlight
different parts of Earth receive. For example, you know that the equator receives much more
solar energy per square foot than do the poles. This is why areas near the equator are much
warmer than areas near the poles. The differences in heating produce convection cells in the
troposphere in the same way as we saw for local winds. Air that moves over warmer regions
warms and rises, and as the air cools, it sinks. This produces an overall movement of heat from
the equator to the polar regions. Without this global circulation of air, the equator would be much
hotter, and the poles would be much colder. The patterns of rising and sinking air in the Hadley
cells also produce global pressure systems
Describe the theory of plate tectonics and the evidence that supports this theory. – ✔✔Wegener
put together several geological observations about the continents. First, he observed that the
shapes of the continents in some cases suggest a “fit”, like puzzle pieces. For example, the east
coast of South America and the west coast of Africa seem to fit together. He also noticed many
rock and fossil similarities between continents. For example, he observed that similar fossils are
found on continents that today are widely separated, but if you put the continents together as
their shapes seem to suggest, the fossils and rocks also match up. Based on these observations,
Wegener proposed the idea of continental drift. According to this idea, the continents were once
joined together into one large, single landmass, but have since drifted away from each other to
their current locations.
Explain how the discovery of seafloor spreading contributed to our understanding of plate
tectonics. – ✔✔Instead of viewing the crust as a single, solid mass, they began to view it as being
broken up into large pieces called tectonic plates. The places where the plates touch are the
places where earthquakes and volcanoes are most likely. In time, the idea of tectonic plates was
combined with other observations to form the theory of plate tectonics. The theory of plate
tectonics is the main unifying theory in geology. According to this theory, Earth’s crust is broken