Pergeseran benua

Hipotesis pergeseran benua (bahasa Inggris: continental drift) merupakan gagasan bahwa benua-benua di Bumi berpindah, terlihat seperti "bergeser" di dasar laut. Meski telah dikemukakan sejak abad ke-16, hipotesis ini baru disampaikan secara ilmiah oleh Alfred L. Wegener dalam buku berjudul The Origin of Continent and Oceans (1912).^[1] Isinya, benua tersusun dari batuan sial yang terapung pada batuan sima yang lebih besar berat jenisnya. Pergerakan benua itu menuju khatulistiwa dan juga ke arah barat.

Wegener mendapati bahwa timur Amerika Selatan cocok jika dihubungkan dengan barat Afrika, memberi petunjuk bahwa semua benua dahulu pernah bersatu. Wegener mencari bebatuan dan fosil di dua sisi benua yang berbatasan dengan Samudra Atlantik untuk membuktikan hipotesisnya. Dia berhasil menemukan bukti-bukti tersebut tetapi tidak dapat menjelaskan mekanisme pergerakan benua dan gagasannya ditentang oleh organisasi seperti American Petroleum Society.^[2] Hipotesisnya tidak diacuhkan hingga kematiannya pada 1930.^[3]

Hipotesis utamanya adalah di bumi pernah ada satu benua raksasa yang disebut Pangaea (artinya "semua daratan") yang dikelilingi oleh Panthalassa ("semua lautan"). Selanjutnya, 200 juta tahun yang lalu Pangaea pecah menjadi benua-benua yang lebih kecil yang kemudian bergerak menuju ke tempatnya seperti yang dijumpai saat ini.

Beberapa ilmuwan dapat menerima konsep ini namun sebagian besar lainnya tidak dapat membayangkan bagaimana satu massa benua yang besar dapat mengapung di atas bumi yang padat dan mengapa ini terjadi. Pemahaman para ilmuwan pengkritik adalah bahwa gaya yang bekerja pada bumi adalah gaya vertikal. Tidaklah mungkin gaya vertikal ini mampu menyebabkan benua yang besar tersebut pecah. Pada masa itu belum dijumpai bukti-bukti yang meyakinkan. Wegener mengumpulkan bukti lainnya berupa kesamaan garis pantai, persamaaan fosil, struktur dan batuan. Namun, tetap saja usaha Wegener sia-sia karena Wagener tidak mampu menjelaskan dan meyakinkan para ahli bahwa gaya utama yang bekerja adalah gaya lateral bukan gaya vertikal.

Pada tahun 1960-an, ditemukan bahwa magma berada di sepanjang garis lempeng tektonik, menandakan dasar laut bergeser seperti yang diperkirakan Wegener.^[4]

Pembuktian

Jack Oliver disebut-sebut sebagai ilmuwan yang membuktikan pergerakan benua melalui pembuktian seismolog dalam tulisannya "Seismology and the New Global Tectonics" pada 1968.^[5]

Referensi

^ U.S. Geological Survey. "Historical perspective". pubs.usgs.gov. Diakses tanggal 27 Desember 2020.
^ Twigger 2014, hlm. 25-16, "Wegener, from an early age, noticed what every schoolchild notices: South America fits into the right angle of west Africa; in fact the land mass of earth all looks as if it was once joined. Wegener searched for evidence of his theory – finding rocks and fossils that matched on either side of the Atlantic Ocean. He provided the evidence but no mechanism and was opposed heatedly by such august organisations as the American Petroleum Society."
^ Twigger 2014, hlm. 25, "Alfred Wegener, a German explorer and scientist, was disbelieved and ridiculed for his continental-drift theory – the theory, put forward in 1912, that the world was fissured, like an infant’s skull, and yet that these fissures were actually fruitful, fructifying with molten magma deep under the sea, expanding, sliding over each other. Wegener was ignored from his untimely death in Greenland in 1930 untul the 1950s, a warning shot to those who would propose a theory that looks right but can’t be easily explained."
^ Twigger 2014, hlm. 26, "The discovery in the 1960s that the sea floor really did spread as Wegener had speculated, with magma bubbling up along tectonic plate lines, finally brought respectability to a theory that had been derided and lampooned. Scientists agreed that circulating hot liquid centre of the earth was how the plates, with the continents sitting on top of them, moved. Just as rice in a pan of boiling water will circulate, so the surface of the earth was in constant movement, shoved by the circulating movement of the magma below."
^ Chang, Kenneth (2011-01-12). "Jack Oliver, Who Proved Continental Drift, Dies at 87 (Published 2011)". The New York Times (dalam bahasa Inggris). ISSN 0362-4331. Diakses tanggal 27 Desember 2020. In 1968, Dr. Oliver, Dr. Isacks and another former graduate student of Dr. Oliver, Lynn Sykes, wrote a paper, “Seismology and the New Global Tectonics,” that put together earthquake evidence from around the world that made a convincing case that continental drift - now called plate tectonics - was indeed occurring.

Daftar Pustaka

Twigger, Robert (2014). Red Nile : A Biography of the World's Greatest River (edisi ke-satu AS). New York: St. Martin's Press. ISBN 978-1-250-05233-9. OCLC 883962326.

Artikel bertopik geologi ini adalah sebuah rintisan. Anda dapat membantu Wikipedia dengan mengembangkannya.

[1] U.S. Geological Survey. "Historical perspective". pubs.usgs.gov. Diakses tanggal 27 Desember 2020.

[FOOTNOTETwigger201425-16-2] Twigger 2014, hlm. 25-16, "Wegener, from an early age, noticed what every schoolchild notices: South America fits into the right angle of west Africa; in fact the land mass of earth all looks as if it was once joined. Wegener searched for evidence of his theory – finding rocks and fossils that matched on either side of the Atlantic Ocean. He provided the evidence but no mechanism and was opposed heatedly by such august organisations as the American Petroleum Society."

[FOOTNOTETwigger201425-3] Twigger 2014, hlm. 25, "Alfred Wegener, a German explorer and scientist, was disbelieved and ridiculed for his continental-drift theory – the theory, put forward in 1912, that the world was fissured, like an infant’s skull, and yet that these fissures were actually fruitful, fructifying with molten magma deep under the sea, expanding, sliding over each other. Wegener was ignored from his untimely death in Greenland in 1930 untul the 1950s, a warning shot to those who would propose a theory that looks right but can’t be easily explained."

[FOOTNOTETwigger201426-4] Twigger 2014, hlm. 26, "The discovery in the 1960s that the sea floor really did spread as Wegener had speculated, with magma bubbling up along tectonic plate lines, finally brought respectability to a theory that had been derided and lampooned. Scientists agreed that circulating hot liquid centre of the earth was how the plates, with the continents sitting on top of them, moved. Just as rice in a pan of boiling water will circulate, so the surface of the earth was in constant movement, shoved by the circulating movement of the magma below."

[5] Chang, Kenneth (2011-01-12). "Jack Oliver, Who Proved Continental Drift, Dies at 87 (Published 2011)". The New York Times (dalam bahasa Inggris). ISSN 0362-4331. Diakses tanggal 27 Desember 2020. In 1968, Dr. Oliver, Dr. Isacks and another former graduate student of Dr. Oliver, Lynn Sykes, wrote a paper, “Seismology and the New Global Tectonics,” that put together earthquake evidence from around the world that made a convincing case that continental drift - now called plate tectonics - was indeed occurring.

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