It is well known that sand absorbs water very easily. If you pour a small amount of water on sand, it will soak it up within moments.
However, seas and oceans always have a large amount of sand beneath them. So, how does this sand not absorb the water above it?
Where does sand come from?
When looking at any beach, we can see large amounts of sand stretching along the coastline.
But where does this sand come from? Contrary to what some might think, the sand on beaches does not originate from the seabed; this is not its primary source.
Beach sand is primarily formed through weathering, erosion, and deposition processes that affect rocks on land near the shoreline.
The constant tides and waves of the sea crash forcefully against these rocks, gradually breaking them down and contributing to the accumulation of sand on the beach.
This process leads to the gradual erosion of rocks, causing them to break down slowly into smaller fragments.
Not only that, but other weathering factors also contribute to the breakdown of rocks near the shores, such as wind, ocean currents, rainfall, temperature fluctuations, and more.
Over time, these rocks disintegrate and accumulate along the coastline in the form of sand. This process does not happen overnight; it takes thousands or even hundreds of thousands of years.
In short, the sand found on beaches is nothing but fragmented rocks specifically, the rocks surrounding the shore.
Where do sand colors come from?
The rocks surrounding the beach are what determine the color and texture of the sand, making beaches around the world look different from one another.
Beach sand is directly linked to the type of rocks in the surrounding area. This is why most beaches worldwide have sand that ranges between shades of yellow and brown.
The reason why sand is yellow and brown
This is because feldspar mineral salts make up about 60% of the Earth's rocks, along with quartz, which is a major component of most rocks. When these rocks break down over time, they produce sand in shades of yellow and brown.
The reason for the formation of green sand
Papakōlea Beach, located on Hawaii Island, is known for its distinctive green sand. This unique color comes from the island’s volcanic rocks, which contain the mineral olivine.
Olivine is a magnesium-iron silicate, and its presence in the eroded volcanic material gives the beach its striking green hue.
The reason why sand is black
Meanwhile, Punaluʻu Beach, also located on Hawaii Island, features black sand. This is due to the presence of basalt rocks surrounding the beach, which are formed from cooled lava flows, giving the sand its distinctive dark color.
The fact that there is sand at the bottom of seas and oceans
What we mentioned earlier applies only to the sand found on beaches, not the sand within the ocean itself.
The seabed of most seas and oceans does not typically contain large amounts of sand; instead, sand is usually concentrated on the surface near the shore.
Additionally, the total amount of sand on beaches is insignificant compared to the vast volume of water in the seas and oceans. As a result, the sand is unable to absorb the surrounding water.
Why does sand not absorb sea and ocean water?
No matter what, sand has a specific saturation limit for water; once it reaches that limit, it can no longer absorb more.
As for the ocean floor, any sand that does settle there is in very small amounts and is not significant enough to absorb seawater.
In fact, sand accumulation on the seabed is typically localized to specific areas. When examining the materials covering the ocean and sea floors, we find that they mostly consist of silt and clay, with only a minimal percentage of sand.
Moreover, these layers of silt, clay, or other sediments on the ocean floor are not very deep. Just beneath them lies a solid rock layer, which is part of the Earth's crust.
This layer is dense, impermeable to water, and serves as the foundation of the ocean floor, effectively preventing water from seeping into the deeper layers of the Earth.
In addition to this natural barrier at the seabed, another crucial factor comes into play the water cycle in nature.
What is the water cycle in nature?
The water cycle in nature is the process that compensates for any water loss. Although this cycle does not have a specific starting point, the best place to begin understanding it is the ocean.
Stages of the water cycle in nature:
The sun's rays heat the water in the oceans, turning it into water vapor. This vapor rises into the atmosphere until it reaches cooler layers, where it condenses and forms clouds.
Air currents then move these clouds across the Earth's surface. Once the clouds become heavy enough, they turn into rain clouds and spread, releasing precipitation.
Some of this rain falls back into the ocean, while some reaches rivers and freshwater lakes. Other portions freeze into ice and later melt, flowing back across the land. Some rainwater seeps into the soil, where it is stored as groundwater.
Most waterways are ultimately interconnected, forming a vast network that directs water back into the ocean.
Even in isolated areas with limited stored groundwater, plants absorb moisture through their roots and release it back into the atmosphere through transpiration.
The same principle applies to beach sand. If sand absorbs some seawater, that water eventually evaporates and returns as rain.
This continuous water cycle ensures that oceans and seas remain full, keeping their water levels relatively stable over thousands of years.
However, scientists predict that ocean levels will rise in the future due to increasing global temperatures.
As polar ice caps melt, the resulting water will contribute to rising sea levels. Still, despite these changes, large bodies of water are far from drying up due to sand absorption.