GEOSCI / ROCK CYCLE
Life of a grain of sand
Follow one grain of quartz from a beach to the seabed, deep underground, into solid rock, up into a mountain, down a river and back to the beach. The grain barely changes. Everything around it does. It stays near the same place on your screen while the world moves around it.
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01 / 16 · The beach
Where the sand is
Beaches hold more loose sand than almost anywhere, but every grain there is a survivor. Soft minerals get ground to clay or dissolve. Quartz is hard and chemically stable, so it lasts. Drag the slider to see who is left.
02 / 16 · The surf
Dragged into the surf
Every wave picks the grain up and drops it again. Over days and years it is nudged along the shore, and slowly dragged out beyond the breakers.
03 / 16 · The seabed
Out to sea
Waves and currents carry the grain offshore. Big, heavy grains drop out first while mud drifts furthest, so the seabed sorts itself. Change the energy and watch it happen.
04 / 16 · A new blanket
A new blanket
Sand and mud keep settling in thin layers. Worms churn the top, but soon the grain is under a fresh blanket, then another, then another.
05 / 16 · Buried
Buried
Sediment keeps raining down. Each new layer buries the grain deeper, where it gets hotter and is squeezed harder. Drag the depth to see what the grain feels.
06 / 16 · Squeezed
Squeezed and heated
Millions of years and thousands of layers later, the weight is immense. Water is squeezed out, minerals dissolve and regrow, and the temperature climbs by roughly 25 °C every kilometre.
07 / 16 · Sandstone
Turning to stone
Squeezing and mineral-rich water turn loose sand into rock, in steps called compaction and cementation. The grain does not change. The gaps around it do. Zoom in and run the clock.
08 / 16 · Plates on the move
The plates move
Zoom out. Far below, the mantle churns and drags the plates above it along at a few centimetres a year. Two plates are heading for each other, and our sandstone is trapped between them. The grain looks smaller because the view is much wider.
09 / 16 · Collision
Pushed up
Colliding tectonic plates fold, crack and lift whole layers of rock into mountains. The grain rises with its layer, from kilometres underground to high above the sea.
10 / 16 · A mountain range
A mountain range
After tens of millions of years of squeezing, the old seabed stands thousands of metres above sea level, right where the grain has ended up: inside the rock of a mountain.
11 / 16 · Weathering
Coming apart
Exposed to rain, roots, wind and sun, the mountain rock starts to weather. Weak minerals rot into clay and the glue between grains dissolves. Pick a process and run the clock.
12 / 16 · Down the slope
Down the slope
Rain beats on the loosened surface. Water gathers into rills that carry sand downhill, the gullies deepen, and the grain starts its way down.
13 / 16 · The river from above
The river from above
Streams join into a river that winds across the plain. From up here the grain is a tiny speck among billions in a muddy ribbon of water. Now fall back into the channel.
14 / 16 · The river
Down the river
In the channel, how a particle travels depends on its size and how fast the water flows. Speed the river up and see what lifts.
15 / 16 · River mouth
Where river meets sea
The river slows as it meets the sea and drops its load, building a delta of channels and sandbars. Waves then spread the sand along the coast.
16 / 16 · Rock cycle
Back to the beach
The grain washes up on a beach, where it began. That loop is one path through the rock cycle. Follow the other paths it could have taken.