Earth Science CER Data Explorer

Background

Earthquakes happen when rock breaks and slips along a fault. How strong the earthquake is depends on how much rock breaks at one time.

At a subduction zone, one plate slides down underneath another. The deeper that rock goes, the hotter it gets and the harder it is squeezed.

Cold rock near the surface is brittle. Brittle means it snaps, like a dry stick. Stress builds up for years, then a large block breaks all at once.

Hot rock deep down is ductile. Ductile means it bends and flows slowly, like warm taffy. Rock that bends does not store as much stress, so when it finally does break, a smaller block moves.

Think about it: if deep rock can only break in smaller pieces, what does that do to the largest magnitude you would expect to find down there?

Background

Energy from the Sun arrives mostly as visible light. That light passes through the atmosphere and warms Earth's surface.

Earth then sends energy back out, but as infrared — heat energy you can feel but not see.

Some gases in the air absorb that outgoing heat and send part of it back down. These are called greenhouse gases. The main ones are carbon dioxide (CO₂), water vapor, and methane.

This is normal and necessary. Without any greenhouse gases at all, Earth's average temperature would be far below freezing.

What has changed is the amount. Burning coal, oil, and natural gas releases extra CO₂. More CO₂ means more outgoing heat gets absorbed instead of escaping, so the average temperature goes up.

Think about it: the table shows temperature going up and down before 1940, then climbing steadily after 1960. What changed?

Background

Two things are raising sea level, and both come from a warmer planet.

1. Thermal expansion. When water warms up, its molecules move faster and spread farther apart. The same amount of water takes up more space. The ocean is very deep, so even a small amount of warming adds up to a real rise.

2. Melting land ice. Glaciers and the ice sheets on Greenland and Antarctica sit on top of land. When they melt, that water runs into the ocean and adds volume that was not there before.

Sea ice is different. Sea ice already floats in the ocean, so it already pushes water aside. When it melts, sea level barely changes — the same way a glass of ice water does not overflow when the ice cubes melt.

Think about it: why does ice on land raise sea level when floating ice does not?

Background

Carbon moves constantly between the air, the ocean, soil, and living things. This is called the carbon cycle.

Plants pull CO₂ out of the air during photosynthesis. Animals breathe CO₂ out, and decaying material releases it too. For thousands of years these moved about the same amount of carbon in each direction, so the level in the air stayed fairly steady.

Fossil fuels break that balance. Coal, oil, and natural gas formed from living things that were buried millions of years ago. All of that carbon sat locked underground, out of the cycle.

Burning fossil fuels puts that carbon back into the air in a couple of hundred years — carbon that took millions of years to store away. The natural processes that remove CO₂ cannot keep up with that speed.

Think about it: the amount added each decade in the table keeps getting bigger. What does that tell you about how fast we are burning fossil fuels?

Background

Gravity is what holds a planet in its orbit. The Sun's gravity pulls on every planet, but that pull gets weaker the farther away the planet is.

A planet close to the Sun feels a strong pull, so it has to move fast to stay in orbit. A planet far out feels a weak pull and moves much more slowly.

Distant planets also have much farther to travel to finish one lap. So they lose twice over: a longer path and a slower speed. That is why Neptune takes 163.7 years to go around once while Mercury takes only 88 days.

Kepler's Third Law puts a number on this. The square of a planet's period is proportional to the cube of its distance, written P² ∝ r³.

Think about it: if you double a planet's distance from the Sun, does its year get twice as long, or more than twice as long?

Background

A claim can sound reasonable and still be wrong. The way to test one is to check it against the data.

This student's reasoning is not crazy. Pressure really does increase with depth. But pressure is not the only thing that increases. Temperature goes up too, and heat is what makes rock ductile — able to bend slowly instead of snapping.

A big earthquake needs a large block of brittle rock to break all at once. Deep rock is too hot to do that.

Think about it: on the Part A graph, are the highest magnitudes at the deepest depths, or somewhere else?