Earth
26 questions tagged Earth — spanning every one of the seven Ws.
What is climate change?
Climate change is the long-term shift in global temperatures and weather patterns, driven mainly by human greenhouse-gas emissions.
What is the water cycle?
The water cycle is the continuous movement of water through evaporation, condensation, and precipitation across Earth.
What is a tsunami?
A tsunami is a series of huge ocean waves, usually caused by an undersea earthquake, that can travel across whole oceans at jet speed.
When did life first appear on Earth?
The earliest known life appeared at least 3.5 billion years ago, in the form of simple single-celled microbes.
Where do most volcanoes occur?
Most of the world volcanoes lie along the Ring of Fire, a horseshoe-shaped zone around the edges of the Pacific Ocean.
Which gas is most common in the air?
Nitrogen makes up about 78% of Earth atmosphere, far more than oxygen, which accounts for around 21%.
How do tides work?
Tides are caused mainly by the Moon gravity pulling on Earth oceans, creating bulges of water that rise and fall as the planet rotates.
How do clouds form?
Clouds form when warm, moist air rises and cools, causing water vapour to condense into tiny droplets around dust particles.
What is the Richter scale?
The Richter scale measures the magnitude of earthquakes on a logarithmic scale.
What is a fossil?
A fossil is the preserved remains or traces of a once-living organism from the distant past.
Which continent is the largest?
Asia is the largest continent, covering about 44.6 million square kilometres and home to around 60 percent of all people.
How old is the Earth?
Earth is about 4.54 billion years old, based on radiometric dating of meteorites and ancient rocks.
Where is the equator?
The equator is the imaginary line at 0 degrees latitude, circling the middle of Earth halfway between the North and South Poles.
How much does the Earth weigh?
Earth’s mass is about 5.97 × 10²⁴ kilograms, or roughly 6 septillion kilograms.
How does geothermal energy work?
Geothermal power plants tap heat from deep underground, using hot water or steam to spin turbines that generate electricity.
How hot is lava?
Lava usually erupts at between about 700 °C and 1,200 °C, depending on its chemistry.
How do mountains form?
Most mountains form when tectonic plates collide and push the crust upward, while others form from volcanic activity or blocks of crust rising along faults.
How do islands form?
Islands form in several ways, including volcanic eruptions from the seabed, coral reefs growing on sunken volcanoes, and land separated from continents by rising seas.
Why do rivers form deltas?
A delta forms when a river slows down as it enters a lake or sea and drops the sediment it has been carrying, building up layers of new land.
Why does the Earth have tectonic plates?
Earth’s outer shell cracked into plates because the hot mantle below slowly convects, and the plates are rigid enough to move as distinct units on top of it.
What is an earthquake swarm?
An earthquake swarm is a series of many small to moderate earthquakes in one area over days to months, with no single dominant main shock.
Which Is the Densest Planet in the Solar System?
Earth is the densest planet in the solar system, with an average density of about 5.51 grams per cubic centimetre.
What is an equinox?
An equinox is one of two moments each year, around 20 March and 22–23 September, when the Sun is directly above the equator and day and night are roughly equal everywhere.
Why does Earth have a magnetic field at all?
Earth’s magnetic field is generated by moving molten iron in its liquid outer core. That flowing, electrically conducting metal acts as a geodynamo.
Why does Earth have seasons?
Earth has seasons because its axis is tilted by about 23.5 degrees as it orbits the Sun. That tilt changes the angle and duration of sunlight through the year.
Which planet is densest?
Earth is the densest planet in the Solar System, with an average density of about 5.51 grams per cubic centimeter. Its iron-rich core helps make it unusually dense.