The Story of Sand
- Jul 30
- 8 min read
Dear Reader,
I started writing this issue just before setting off on a trip to Goa, when I was dreaming of the sand and the monsoons along the coast. There’s something mesmerising about sand, especially at a beach — embedded with half-weathered shells, or rolled up into little balls by the crabs, or braided into river-like patterns by the channels that meet the sea. I’m often reminded of this verse:
“To see a world in a grain of sand
And a heaven in a wild flower,
Hold infinity in the palm of your hand
And eternity in an hour.”
~ Auguries of Innocence, William Blake
William Blake writes of a world that can be seen in a mere grain of sand. To think that the infinite mysteries of the Universe can be unravelled using the tiniest of clues. A grain of sand captures the tides of Time from the grinding down of mighty mountains, the eddies and ripples of rivers, the ever-shifting reaches of a delta, to the restless ebb of the oceans.
In this edition, I hope to trace the journey of sand from weathered material to the depths of the ocean, from crushed coral reefs to smartphone screens, and everything in between, to explore the geological, ecological and human histories imprinted upon these particles.
The Journey of Sand
"In every curving beach, in every grain of sand, there is a story of the Earth." ~Rachel Carson.
We often associate coastlines with sand, yet sand forms in a variety of settings. Over millennia, rocks are weathered and eroded by rainwater, ice, heat, wind, waves, and even plants and animals, breaking down into smaller particles. Any particle between 0.06 and 2 millimetres is classified as sand; anything larger is a pebble, and anything smaller is silt or clay. Weathered rocks contain minerals, some of which are soluble, and are lost in transit. Quartz and feldspar are among the toughest components of rock, and sand often comprises these two minerals. If the quartz contains iron oxide, it takes on a light brown colour, whereas feldspar is a light tan, and together, they create the rippled, coloured hues across sandy riverbanks, beaches and deserts. Volcanic rock also weathers down to form sand. Black or darker sands contain obsidian or volcanic glass; greenish sands are rich in olivine; reddish sands are tinted with iron oxide.
The role of rivers, as they tumble from source to sea, is often overlooked when we speak of sand formation. In the early, fast-moving stages of a river, it tears down the ambition of rocky mountains into coarse materials and carries them downslope. As it encounters obstacles, the river deposits sandy material along its meanders, or along its channel, to form islands of sand and silt, where plants can take root. These islands offer temporary refuge or breeding and hunting grounds for riverine creatures. In India, the Chambal river’s sandy, midstream islands are crucial habitats for the gharials.
When the river winds its way past the mountains and enters the plains, it creates immense fans of fertile, alluvial silt, and carries the coarser sand particles further along. Finally, as the river loses momentum, it deposits the sand along the delta before it embraces the sea. The deltaic sand creates a barrier between freshwater and the brackish and salty currents. Sand bars and spits are colonised by palm, mangrove or intertidal vegetation to form critical wildlife habitats. These natural, sandy barriers also prevent coastal erosion, mitigate flooding, and can dampen the effect of cyclones, extreme weather events, tsunamis, and storms.
Desert sands tell different stories of weathered materials carried across distances by wind or by rivers or streams in distant, less arid times, before the area became a desert. Wind-borne sand, in turn, can blast rocks to create incredible, mushroom-like sculptures that are whittled away, or sand-blasted to create more sand. River-borne sand speaks of a time when a stream carved its way through the landscape, but eventually dried up. With no vegetation to hold onto the soil, the lighter silt and clay particles were blown away by the wind, leaving behind coarse sands. Across deserts, the wind scythes its way through the sand to create an ever-shifting pattern of ripples and dunes.
Seashores are formed by sand brought in by rivers, with some additional processes at play. Ocean waves pulverise shells, hard marine organisms, single-celled foraminifera, and coral reefs into sand. As parrotfish graze on the reef algae, they chomp on coral, and later, poop it out as white sand. Even here, the sands continue to shift, carried along the coastlines by currents, tides and the wind, creating ephemeral features such as ripple marks, beach cusps, crescents, micro-cliffs, sand ridges, runnels, and dunes.
If you’ve ever snorkelled or dived along coastlines, you’ve been exploring the sandy continental shelves fringed by coral colonies. Where does this sand come from? Interestingly, land-borne sediments become finer with distance from the coast, with sand restricted to wave-agitated shallow stretches, and the silt and clay carried further offshore. Yet only some of the sand in which the sea cucumbers and starfish hide was carried by rivers and currents. 60-70% of the sand is much more ancient, likely deposited during the last ice age, when the sea level was 100–120 m lower than it is now.
In some instances, sand may tumble from beaches into the ocean depths, from the rims of submarine canyons — steep-sided valleys created by underwater turbidity currents. If too much beach sand accumulates near the mouth of the canyon, gravity destabilizes the sand, causing an underwater landslide. Submarine canyons are present along all coastlines in the world and represent an important source of beach sediment reaching the deep ocean floor.
These are some of the natural journeys of sand, unhurried, unhindered, and uninterrupted. Yet the journey of sand across a human-dominated landscape is very different!
If you’ve ever snorkelled or dived along coastlines, you’ve been exploring the sandy continental shelves fringed by coral colonies. Where does this sand come from? Interestingly, land-borne sediments become finer with distance from the coast, with sand restricted to wave-agitated shallow stretches, and the silt and clay carried further offshore. Yet only some of the sand in which the sea cucumbers and starfish hide was carried by rivers and currents. 60-70% of the sand is much more ancient, likely deposited during the last ice age, when the sea level was 100–120 m lower than it is now.
In some instances, sand may tumble from beaches into the ocean depths, from the rims of submarine canyons — steep-sided valleys created by underwater turbidity currents. If too much beach sand accumulates near the mouth of the canyon, gravity destabilizes the sand, causing an underwater landslide. Submarine canyons are present along all coastlines in the world and represent an important source of beach sediment reaching the deep ocean floor.
These are some of the natural journeys of sand, unhurried, unhindered, and uninterrupted. Yet the journey of sand across a human-dominated landscape is very different!
Sand, Interrupted.
Since early civilisation, humans have found myriad uses for sand: to grind and polish ancient tools and weapons, to filter water, and to measure time. As human history raced on, sand was melted to create glass, and mixed with cement and water into concrete — our glass-and-concrete buildings are ambitious sandcastles, linked by sand-glazed asphalt roads, running on sand-derived silicon chips.
After water, sand is our most exploited resource. Exploited, not utilized, because for all the sand we see swirling across vast deserts, there’s a severe shortage of sand.
Desert sand is often too smooth, too well-eroded to lock together into stable, hard concrete. Concrete requires the angular, coarse grains, the river-forged sand, and for decades, we’ve been stripping away riverbeds, deltas and beaches, faster than the sand can be replenished. Rapid urbanisation, coupled with weak sand extraction laws, has led to a rapid depletion of this resource.
Beyond infrastructure, we’re also expanding our coastal reaches for more real estate. Dubai’s artificial palm-shaped islands are literal beachfront sandcastles. Since 1965, Singapore’s territory has been expanded by roughly 25% — by “reclaiming” or concretising shallow water and swamps to create urban infrastructure to accommodate a booming population. Nigeria’s largest city, Lagos, is extending its shoreline by 2,400 acres or 9.7 sq.km further into the Atlantic. China has been adding hundreds of coastal miles and building islands for luxury resorts. Hong Kong has dredged up its seafloor sand to create more land. In 2025, the Maldives began shoring up its coastal defences with a land reclamation project, throwing in a new airport for good measure. Jakarta in Indonesia is rapidly subsiding, and they’re building 17 offshore islands as defence against rising sea levels. In Mumbai, India, a 111-hectare stretch has been reclaimed from the ocean to build an 8-lane freeway to connect the bustling city’s north and south halves.
Ocean dredging has damaged coral reefs in Florida, the Persian Gulf, and Kenya, wiped out or polluted coastal wetlands in Mumbai and China, and severely affected fisherfolk livelihoods in Cambodia and Malaysia.
From 1985-2016, coastlines around the world added 33,700 sq. km of land and lost 20,135 sq. km, with a net gain of 13,565 sq. km, as per a satellite data study by a group of Dutch researchers. A decade on, one can only imagine how this battle between Nature and human hubris continues.
As coastal and seafloor sand dredging is more expensive, construction sand is often dredged from rivers. In Vietnam, with over 20 million inhabitants and paddy cultivation that feeds much of Southeast Asia, sand mining, dam building and climate change have wreaked havoc along the Mekong delta. As the Mekong delta is shared by Cambodia and Laos, sand mining affects critical river flows across this geography. A similar tragedy is unfolding along Myanmar’s Ayeyarwady river.
In India, news channels are flooded with stories about the sand mafia, with almost every major river across the country being illegally mined — and an ever-mounting human toll indicates just how precious and precarious the resource is. Sand trade violence has also been reported in Mexico, South Africa, Indonesia, Kenya, Gambia, and the list goes on.
River dredging also has an ecological cost. Without sand, rivers cannot form spits and bars to slow down their flow, and may rapidly erode their upper stretches. This results in river banks collapsing, taking farmlands and settlements with them. Sand dredging may cause a river to shift its course drastically, affecting the formation of fertile, alluvial plains and agricultural yields. If dredging occurs near river-fed lakes, the lake is more susceptible to drought, and it affects river fisheries. Churned-up sediment muddies river water, blocks sunlight from reaching the underwater vegetation, and suffocates or starves fish. Further downstream, a sand-depleted river affects the delta, causing severe coastal erosion and saltwater intrusion into paddy fields and other coastal croplands.
At an ecosystem level, the sand in rivers, deltas and coastal areas provides essential ecosystem functions such as water filtration, river flow regulation, shoreline protection from erosion and storm surges, prevention of coastal aquifer salinization, and biodiversity sustenance. This is classified as “alive” sand.
In a sense, sand is a renewable resource, but not if our rates of extraction far exceed the rate of recharge. Yet after extraction, if sand is transformed into glass, concrete, or asphalt, it is considered “dead” sand; it is lost from natural systems and cannot break down to form sand again. The uses for alive and dead sand directly compete with each other, and development is often prioritized over everything else. When sand is left within ecosystems, it underpins livelihoods, water security, and food systems — the very natural equilibrium our development models should strive for!
