30 Earth Science Bell Ringers With Answers (Grades 6–12)

Igneous rock forms when magma or lava cools and hardens. Sedimentary rock forms when sediments are compacted and cemented together (or when minerals precipitate out of water). Metamorphic rock forms when existing rock is changed by heat and pressure without fully melting.

Crystal size tells you cooling speed. Granite cooled slowly underground (intrusive), so crystals had time to grow large. Basalt cooled quickly at or near the surface (extrusive), so crystals stayed tiny.

Its hardness is between 5.5 and 7, so about 6. Orthoclase feldspar, which is a 6 on the Mohs scale, fits.

Coal. A mineral must be naturally occurring, inorganic, solid, with a definite chemical composition and an orderly crystal structure. Coal forms from ancient plant material, so it’s organic. It’s classified as a sedimentary rock.

Limestone is made mostly of calcite (calcium carbonate). The acid reacts with it and releases carbon dioxide gas, which makes the bubbles. Granite doesn’t contain much calcite, so it doesn’t react.

It would have to be buried deep enough to melt into magma, then cool and crystallize. It might pass through a metamorphic stage on the way, but melting is the step that makes it igneous.

Divergent: plates move apart. Convergent: plates move toward each other. Transform: plates slide past each other sideways.

It’s a divergent boundary. Plates are pulling apart, magma rises, and new oceanic crust forms. This is seafloor spreading. Iceland sits on top of this ridge.

Oceanic crust is denser than continental crust, so it sinks (subducts) beneath it. This creates a deep trench and a chain of volcanoes on land, like the Andes.

The Indian plate collided with the Eurasian plate. This is a continental-continental convergent boundary. Neither plate sinks easily because continental crust is too buoyant, so the crust crumples, folds, and thickens upward into huge mountains.

A transform boundary. The Pacific plate and the North American plate slide past each other. Stress releases as earthquakes, but no crust is created or subducted, so little magma forms.

Any two: matching coastlines (South America and Africa), matching fossils on separate continents (such as Mesosaurus and Glossopteris), matching rock formations and mountain ranges, and evidence of past glaciers in places that are warm today.

What was missing: a convincing mechanism for how continents move. Seafloor spreading evidence later filled that gap and led to the theory of plate tectonics.

Weather is the short-term condition of the atmosphere (today is rainy and 60°F). Climate is the long-term average pattern for a region, usually measured over decades (the Southeast has hot, humid summers).

Expect thunderstorms or heavy rain, a drop in temperature, and a wind shift. Cold, dense air pushes under the warm air and forces it to rise quickly. The rising air cools, water vapor condenses, and tall cumulonimbus clouds form.

The difference in distance to the Sun is tiny and doesn’t matter. In the lower atmosphere, temperature generally drops as altitude increases. The air is heated mostly by the ground, air pressure is lower up high, and rising air expands and cools.

Land heats up faster than water during the day. Warm air over the land rises, and cooler air from over the water moves in to replace it. That’s a sea breeze.

Counterclockwise (seen from above). The Coriolis effect, caused by Earth’s rotation, deflects moving air to the right in the Northern Hemisphere, which sets up the counterclockwise spin around low pressure. In the Southern Hemisphere they spin clockwise.

Sunlight passes through the atmosphere and warms Earth’s surface. The surface gives off heat as infrared radiation. Greenhouse gases such as water vapor, carbon dioxide, and methane absorb some of that infrared energy and send part of it back toward the surface, keeping the lower atmosphere warmer than it would be otherwise.

Any four: evaporation, transpiration, condensation, precipitation, runoff, infiltration, collection. The main energy source is the Sun. Gravity brings precipitation and runoff back down.

From the air. Water vapor touches the cold glass, cools, and condenses into liquid droplets. The glass isn’t leaking.

Most fresh water is frozen in glaciers and ice caps. Most of the rest is groundwater. Lakes and rivers hold only a tiny share.

Pavement doesn’t let water soak in, so there’s more runoff and less infiltration. That can cause flooding. The forest floor lets water soak in and recharge groundwater.

Transpiration is the release of water vapor from plants, mostly through tiny openings in the leaves called stomata.

When ocean water evaporates, only the water becomes vapor. The salt stays behind in the ocean. The vapor later condenses and falls as fresh water.

The tilt of Earth’s axis (about 23.5°). As Earth orbits the Sun, each hemisphere takes turns being tilted toward the Sun, which gives it more direct sunlight and longer days.

Teacher note: It is not distance. Earth is actually closest to the Sun in early January, during Northern Hemisphere winter.

A full moon. The order is new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent. The full cycle takes about 29.5 days.

The Moon rotates once on its axis in the same time it takes to orbit Earth. This is called synchronous rotation, and it’s caused by tidal locking.

150,000,000 ÷ 300,000 = 500 seconds, which is about 8 minutes and 20 seconds.

Solar eclipse: Sun, Moon, Earth. The Moon is between the Sun and Earth and casts its shadow on Earth. It can only happen at a new moon.

Lunar eclipse: Sun, Earth, Moon. Earth is in the middle and its shadow falls on the Moon. It can only happen at a full moon.

Teacher note: Eclipses don’t happen every month because the Moon’s orbit is tilted about 5° compared to Earth’s orbit, so the three usually don’t line up exactly.

Venus has a thick atmosphere made mostly of carbon dioxide, which traps heat in a runaway greenhouse effect. Mercury has almost no atmosphere, so its heat escapes.