We have leap years because Earth takes about 365.25 days to orbit the sun, not exactly 365 days. By adding an extra day every 4 years, we keep our calendar aligned with Earth's position in its orbit around the sun.

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Earth has seasons because its axis is tilted at about 23.5 degrees as it orbits the sun, causing different parts of Earth to receive more or less direct sunlight at different times of year. This tilt, not Earth's distance from the sun, is what creates summer, fall, winter, and spring.

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Earthquakes are caused by the sudden release of energy stored in rocks beneath Earth's surface, usually when tectonic plates shift and collide. This movement creates seismic waves that shake the ground.

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Volcanoes erupt when hot, molten rock called magma builds up beneath Earth's surface and pressure forces it upward through cracks in the crust. When the magma reaches the surface, it erupts as lava, ash, and gases.

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Ocean tides are caused mainly by the gravitational pull of the Moon and the Sun on Earth's oceans. The Moon has the strongest effect because it is much closer to Earth than the Sun.

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