Material Pembentuk Kerak Bumi pada litosfer/Material Forming the Earth's crust on the lithosphere FOR CLASS X GEOGRAPHY
Material Pembentuk Kerak Bumi pada litosfer
(Sumber: Sudibyakto, H. A. 2009. Geografi.Jakarta: Departemen Pendidikan Nasional.)
Kerak Bumi dapat dibedakan atas kerak benua dan kerak samudera. Kerak benua selain lebih tebal juga lebih beragam dibandingkan kerak samudera. Material pembentuk kerak benua pada lapisan atas berupa batuan granit ringan sedangkan lapisan bawah terbentuk dari material batuan basal yang lebih rapat. Berdasarkan umur geologi, strata atau lapisan ini terbentuk dalam berbagai jaman dan melalui berbagai proses. Batuan yang paling tua ditemukan pada jaman prekambium. Batuan yang lebih muda terbentuk pada jaman ketika terjadi pembentukan pegunungan.
Lapisan kerak samudera paling atas tersusun atas material sedimen yang tebalnya mencapai 800 meter. Kerak samudera mengalami pembaharuan terus menerus oleh kegiatan gunung api di sepanjang celah dasar laut. Celah dasar laut yang memanjang ini biasa disebut dengan pematang tengah samudera. Dilihat dari umur geologisnya, lapisan ini termasuk muda dengan umur kurang dari 200 juta tahun bila dibandingkan kerak benua yang berumur sampai 3,8 miliar tahun.
Kerak benua menjulang lebih tinggi daripada kerak samudera. Hal ini disebabkan kerak benua yang tersusun oleh material granit yang ringan dan kerak samudera yang tersusun oleh batuan basal yang berat. Kerak benua berada rata 850 meter di atas permukaan laut sedangkan kerak samudera berada rata 3.800 meter di bawah permukaan laut. Akibat adanya gerusan oleh tenaga angin dan limpasan air hujan pada permukaan kerak terbentuk hamparan pasir, debu dan lumpur. Material ini kemudian hanyut terbawa aliran air ke laut dan membentuk lapisan sedimen di dasar samudera. Di bawah lapisan batuan sedimen ini terdapat lapisan batuan basal yang berupa lava bantal, retas vertical dan gabro berbutir kasar.
Material Forming the Earth's crust on the lithosphere
(Source: Sudibyakto, HA 2009. Geografi.Jakarta: Ministry of Education.)
Earth's crust can be distinguished on the continental crust and the oceanic crust. Thicker than continental crust is also more diverse than the oceanic crust. The material forming the upper layer of the continental crust in the form of lighter granitic rocks, while the bottom layer is formed from a material denser basalt rock. Based on the geological age, strata or layers are formed in different timesand through different processes. The oldest rocks found onprekambium era. Younger rocks formed at the time when the formation of mountains.
The top layer of the oceanic crust is composed of a thicksedimentary material reaches 800 meters. Oceanic crust undergocontinuous renewal by volcanic activity along the rift in the ocean floor. Slit lengthwise seabed is commonly called the bund the ocean. Judging from geological age, this layer include young age of less than 200 million years of continental crust compared to 3.8billion years old.
Continental crust is soaring higher than oceanic crust. This is due tothe continental crust is composed of granite material that is lightweight and oceanic crust composed of basalt rock heavy.Average continental crust is 850 meters above sea level while theoceanic crust is 3,800 meters below mean sea level. As a result ofscouring by wind power and rainwater runoff crust formed on the surface of the sand, dust and mud. This material is then carried away by the flow of water into the sea and form a layer of sedimenton the ocean floor. At the bottom layer there is a layer of sedimentary rock is basalt rock in the form of pillow lava, verticaldikes and coarse grained gabbro.
(Source: Sudibyakto, HA 2009. Geografi.Jakarta: Ministry of Education.)
Earth's crust can be distinguished on the continental crust and the oceanic crust. Thicker than continental crust is also more diverse than the oceanic crust. The material forming the upper layer of the continental crust in the form of lighter granitic rocks, while the bottom layer is formed from a material denser basalt rock. Based on the geological age, strata or layers are formed in different timesand through different processes. The oldest rocks found onprekambium era. Younger rocks formed at the time when the formation of mountains.
The top layer of the oceanic crust is composed of a thicksedimentary material reaches 800 meters. Oceanic crust undergocontinuous renewal by volcanic activity along the rift in the ocean floor. Slit lengthwise seabed is commonly called the bund the ocean. Judging from geological age, this layer include young age of less than 200 million years of continental crust compared to 3.8billion years old.
Continental crust is soaring higher than oceanic crust. This is due tothe continental crust is composed of granite material that is lightweight and oceanic crust composed of basalt rock heavy.Average continental crust is 850 meters above sea level while theoceanic crust is 3,800 meters below mean sea level. As a result ofscouring by wind power and rainwater runoff crust formed on the surface of the sand, dust and mud. This material is then carried away by the flow of water into the sea and form a layer of sedimenton the ocean floor. At the bottom layer there is a layer of sedimentary rock is basalt rock in the form of pillow lava, verticaldikes and coarse grained gabbro.
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