Earth Science

~7 mins

Earth Science is the study of our planet and its systems, including geology, meteorology, oceanography, and environmental science. It explores how Earth's processes shape landscapes, climate, and life itself.

1) Earth science exists because the planet is active, not static. It studies all parts of Earth: the solid rock (called the geosphere), the water in oceans and rivers (hydrosphere), the air (atmosphere), the ice in glaciers and poles (cryosphere), and living things (biosphere). None of these exist alone — a volcanic eruption (geosphere) can put ash into the air (atmosphere), change rainfall (hydrosphere), melt ice (cryosphere), and affect crops and people (biosphere). Earth science matters because it looks at those connections as one system. Example: The 2010 Eyjafjallajökull volcano in Iceland shut down European air travel when ash clouds disrupted weather patterns across multiple countries.

2) Deep time means the unimaginably long history of Earth. Human lives measure time in decades or centuries, but Earth is about 4.54 billion years old. To understand that, scientists use two main methods: radiometric dating and relative dating. Radiometric dating measures how unstable atoms (like uranium) slowly change into other atoms (like lead) at fixed rates, giving ages in millions of years. Relative dating compares rock layers — older ones lie below younger ones unless disturbed. Using both, we know the dinosaurs disappeared about 66 million years ago and that the Himalayas started rising only 50 million years ago. Example: Carbon-14 dating can tell us when a tree died thousands of years ago, whilst uranium-lead dating reveals when rocks formed billions of years ago.

3) The rock cycle is the way Earth recycles its solid material. Rocks come in three main types. Igneous rocks form when molten rock (magma) cools — granite (slow cooling underground) and basalt (fast cooling at the surface) are examples. Sedimentary rocks form when bits of other rocks or shells get cemented together, like sandstone or limestone. Metamorphic rocks form when heat and pressure change existing rocks, like slate from shale or marble from limestone. Over time, any rock can change into another: a mountain erodes into sand (sedimentary), buries deep and hardens (metamorphic), melts and erupts (igneous), then the cycle repeats. Example: The white cliffs of Dover are limestone made from ancient sea creatures, whilst the marble in the Taj Mahal was limestone transformed by heat and pressure.

4) Plate tectonics is the idea that Earth's outer shell (called the lithosphere) is broken into giant slabs, or plates, that slowly move on softer rock beneath (the asthenosphere). Heat inside Earth makes rock flow slowly like thick syrup — hot rock rises, cool rock sinks. This pushes plates apart at mid-ocean ridges (like the Mid-Atlantic Ridge), drags them down into the mantle at trenches (like near Japan), or grinds them sideways past each other (like the San Andreas Fault in California). This movement is why we have earthquakes, volcanoes, mountains, and new ocean floors. Example: The Atlantic Ocean grows wider by about 2.5 centimetres per year as the Mid-Atlantic Ridge pushes Europe and America apart.

5) Earthquakes happen when stress builds up in rocks along faults (cracks in Earth's crust) and is suddenly released. Imagine bending a stick until it snaps — the stored energy shoots out as vibrations called seismic waves. There are fast-moving primary waves (P-waves) that compress rock, slower secondary waves (S-waves) that shake side to side, and surface waves that roll along the ground and cause most damage. The magnitude (measured on scales like Richter or moment magnitude) tells us how much energy was released, while intensity tells us how strong the shaking felt. Japan and Chile face constant quakes because they sit where plates collide. Example: The 2011 Tōhoku earthquake in Japan was magnitude 9.1 and moved the entire island of Honshu 2.4 metres eastward.

6) Volcanoes are Earth's pressure valves. Deep inside, heat melts rock into magma, which rises because it is lighter than solid rock. If the magma reaches the surface, it erupts. Some eruptions are gentle, like in Hawai'i, where runny basaltic lava flows steadily. Others are explosive, like Mount Vesuvius, because sticky magma traps gas until it bursts. Volcanoes are destructive — Pompeii was buried in AD 79 — but also constructive. Volcanic ash breaks down into fertile soils; that's why people farm near Mount Etna despite the risk. Example: Hawai'i's Kilauea volcano creates new land as lava flows into the ocean and hardens, whilst Mount Vesuvius remains dangerous to the 3 million people living nearby.

Related: Volcano | Magma | Mount Vesuvius

7) Mountains form mainly at plate boundaries. When two continents collide, their crust crumples and pushes upward, forming ranges like the Himalayas (India colliding with Asia). Volcanoes can also build mountains, like Mount Fuji in Japan. Over millions of years, erosion by rivers and glaciers carves mountains down, carrying sediments to lowlands. Mountains are a balance between building up (tectonics) and wearing down (erosion). Example: Mount Everest grows about 4 millimetres per year as India continues pushing into Asia, but erosion keeps it from growing much taller.

Related: Mountain formation | Himalayas | Orogeny

8) Weathering is the breakdown of rocks where they are. There are two main kinds. Physical weathering breaks rock by force: ice wedges into cracks, expands, and splits stone; roots pry rocks apart. Chemical weathering dissolves minerals: rainwater, slightly acidic with carbon dioxide, eats away limestone to form caves. Erosion is different — it moves the weathered material, by rivers, wind, glaciers, or waves. The Grand Canyon shows weathering plus erosion over millions of years. Example: The limestone caves of Carlsbad Caverns formed when acidic groundwater dissolved rock over millions of years, whilst frost wedging splits rocks in mountain peaks every winter.

Related: Weathering | Erosion | Grand Canyon

9) Soil is the thin living skin of Earth, made of broken rock mixed with water, air, and organic matter (decayed plants and animals). It forms slowly, sometimes only a few centimetres over centuries. Soil is layered: the dark topsoil is rich with life, while deeper layers hold minerals leached down. Fertile river valley soils made Egypt's civilisation possible, while deserts lack soil and remain barren. Without soil, plants and humans alike could not survive. Example: It takes about 500 years to form 2.5 centimetres of topsoil, but intensive farming can erode that same amount in just a few decades.

Related: Soil | Soil formation | Topsoil

10) The water cycle explains how water is constantly moving around Earth. The Sun heats oceans, lakes, and rivers, causing evaporation. Water vapour rises, cools, and condenses into clouds. It falls as rain or snow, flows downhill in rivers, seeps underground, or freezes in glaciers, before returning to the ocean. This endless loop keeps Earth habitable. Storms happen because evaporated water stores hidden energy, which is released when vapour condenses, powering rain and thunder. Example: A single raindrop may evaporate from the Pacific, form clouds over the Rockies, fall as snow in Colorado, melt into the Colorado River, and flow to the Gulf of California.

11) Rivers are nature's conveyor belts. They gather water from rain and melting snow, then carry sediment (sand, gravel, mud) downstream. Rivers carve valleys in mountains and drop sediments in lowlands. On wide floodplains, rivers meander (curve), sometimes cutting off loops to make oxbow lakes. Deltas like the Nile's form where rivers meet seas, dropping their loads. Flooding can destroy, but it also renews soil, which is why people settle near rivers despite the risks. Example: The Mississippi River carries 550 million tonnes of sediment to the Gulf of Mexico each year, building Louisiana's delta whilst the Colorado River carved the Grand Canyon.

Related: River | River delta | Meandering

12) Groundwater is the water stored in spaces between soil and rock underground. Layers of rock that hold water are called aquifers. When tapped by wells, aquifers provide drinking water and irrigation. But if water is pumped faster than it recharges, the water table (the level below which ground is saturated) sinks, wells dry, and land can collapse (subsidence). California's Central Valley has sunk by metres because of over-pumping. Example: The Ogallala Aquifer beneath the Great Plains provides water for 30% of US irrigation but is being drained 8 times faster than it refills.

Related: Groundwater | Aquifer | Water table

13) The ocean covers over 70% of Earth and drives climate. It has layers: warm surface water, colder deep water, and near-freezing abyss. Currents move heat around the globe: the Gulf Stream carries warmth from the tropics to Europe, keeping winters milder than in Canada at the same latitude. The ocean stores carbon dioxide, produces oxygen through plankton, and feeds billions of people. Without it, climate would swing wildly, and life would collapse. Example: London is at the same latitude as Labrador, Canada, but stays 5-10°C warmer in winter thanks to the Gulf Stream bringing tropical heat northward.

Related: Ocean | Gulf Stream | Ocean currents

14) Glaciers are rivers of ice that flow slowly downhill where snow builds faster than it melts. As they creep, they grind rock, carving U-shaped valleys and fjords. They also store fresh water: the Himalayas' glaciers feed rivers that billions rely on. Today, glaciers are shrinking with warming climate, raising sea levels and threatening coastal cities. Example: Norway's fjords were carved by glaciers during ice ages, whilst the Ganges River depends on Himalayan glacial melt to supply water for 400 million people in India and Bangladesh.

Related: Glacier | Fjord | Glacial valley

15) The atmosphere is the blanket of gases surrounding Earth, about 78% nitrogen, 21% oxygen, with small amounts of argon, carbon dioxide, and others. It shields us from radiation, burns up meteors, and keeps heat in through the greenhouse effect. Without the atmosphere, Earth would swing from boiling hot days to freezing nights, like the Moon. Example: The ozone layer in the stratosphere blocks harmful UV radiation, whilst greenhouse gases like carbon dioxide trap enough heat to keep Earth's average temperature at 15°C instead of -18°C.

16) Weather is the short-term state of the atmosphere — sun, rain, wind, storms. It happens because the Sun heats Earth unevenly, creating differences in air pressure that move air. Warm air rises, cool air sinks, winds blow, and water vapour makes clouds and rain. A thunderstorm is just the atmosphere balancing heat and moisture in dramatic fashion. Example: A typical thunderstorm releases energy equivalent to ten Hiroshima bombs, whilst hurricanes can release energy equal to 200 times the world's electrical generating capacity.

17) Climate is the long-term average of weather in a region. The Sahara is dry because high-pressure air there suppresses rain. The Amazon is wet because warm air rises and cools, dropping water daily. Human activity now alters climate by adding greenhouse gases, trapping more heat, shifting rainfall, and melting ice. Weather is today; climate is centuries. Example: London's climate has warmed 2°C since 1900, changing from occasional snow to rare snow, whilst the Sahara was green grassland just 6,000 years ago.

18) Natural resources like minerals, fossil fuels, and metals come from Earth's crust. Coal and oil formed from ancient plants buried and cooked under pressure. Copper, iron, and gold formed in molten and hydrothermal processes deep inside Earth. These resources power industry and technology, but they are finite. Mining too much scars land and pollutes water, forcing societies to balance need with sustainability. Example: Saudi Arabia's oil formed from marine plankton 150 million years ago, whilst Chile's copper deposits formed when volcanic activity concentrated metals in the Andes.

19) Hazards like hurricanes, earthquakes, tsunamis, and droughts are Earth's way of releasing energy. A tsunami is a giant sea wave triggered by undersea quakes or landslides, crossing oceans at jet speed. Droughts starve land when rainfall stops. Hazards remind us Earth is not built for human comfort — we adapt to it, not the other way around. Example: The 2004 Indian Ocean tsunami travelled at 800 km/h across the ocean, reaching shores hours later with waves up to 30 metres high, whilst Australia's Millennium Drought lasted 13 years.

Related: Natural disasters | Tsunami | Drought

20) Earth science is practical because it shapes survival. Predicting quakes, mapping groundwater, forecasting hurricanes, modelling climate — all protect lives. Building codes in Tokyo, flood defences in the Netherlands, and solar farms in deserts all rely on Earth science. Knowing how the planet works is not abstract curiosity but a guide for living wisely on it. Example: Japan's earthquake early warning system gives seconds to minutes of advance notice, whilst the Netherlands' Delta Works protect 9 million people below sea level from flooding.

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