Kenapa air laut asin, tapi air sungai tidak?

Why is the sea salty but river water isn't?

Justru sungai yang membuat laut asin: air hujan melarutkan mineral batuan, sungai membawanya ke laut, lalu matahari menguapkan airnya dan meninggalkan garam selama miliaran tahun.

Short-nya segera tayang di YouTube @geegit

Penjelasannya

Setiap detik, ribuan sungai air tawar menuangkan jutaan liter air ke laut. Lalu kenapa laut asin, sementara sungai tidak? Ironisnya, sungai justru penyebab laut menjadi asin.

Air hujan menyerap karbon dioksida dari udara sehingga sedikit asam. Saat jatuh ke darat, air itu perlahan melapukkan batuan dan melarutkan mineral, termasuk natrium dan klorida, yang lalu dibawa sungai ke laut. Air sungai terasa tawar hanya karena kadar mineralnya sangat kecil, kurang dari seperseratus persen.

Begitu sampai di laut, matahari menguapkan air murni kembali menjadi awan dan meninggalkan garamnya. Setelah hampir empat miliar tahun "penyulingan" oleh matahari, lautan menjadi bank garam terbesar di planet ini.

Diagram dari video

Diagram GeeGit: Every second, thousands of freshwater rivers pour millions of gallons into the oceans. So why is the sea salty, but rivers aren't? — “Every second, thousands of freshwater rivers pour millions of gallons into the oceans. So why is the sea salty, but rivers aren't?”

Diagram GeeGit: This weathering dissolves trace minerals, including sodium and chloride, which rivers carry out to sea. — “This weathering dissolves trace minerals, including sodium and chloride, which rivers carry out to sea.”

Diagram GeeGit: After nearly four billion years of solar distillation, our oceans became the planet's ultimate salt bank. — “After nearly four billion years of solar distillation, our oceans became the planet's ultimate salt bank.”

Transkrip video (English)

Every second, thousands of freshwater rivers pour millions of gallons into the oceans. So why is the sea salty, but rivers aren't?

The ironic twist is: rivers are the exact reason the ocean is salty in the first place.

Rainwater absorbs carbon dioxide from the air, making it slightly acidic. As it falls on land, it slowly breaks down rocks.

This weathering dissolves trace minerals, including sodium and chloride, which rivers carry out to sea.

Rivers taste fresh only because that mineral concentration is tiny: less than one hundredth of a percent.

Once water reaches the ocean, the sun evaporates pure water back into clouds, leaving every grain of salt behind.

After nearly four billion years of solar distillation, our oceans became the planet's ultimate salt bank.

Sumber

U.S. Geological Survey (USGS)
NOAA Ocean Science

Diagram digambar ulang dan disederhanakan oleh GeeGit. Narasi video: suara AI.

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