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Continental drift is a highly supported scientific theory, originating in the early 20th century, that Earth's continents move or drift relative to each other over geologic time. [1] The theory of continental drift has since been validated and incorporated into the science of plate tectonics , which studies the movement of the continents as ...
Drillcores into the crust on these ridge flanks allowed dating of the early and of the older anomalies. This in turn allowed design of a predicted geomagnetic time scale. [ 9 ] With time, investigations married land and marine data to produce an accurate geomagnetic reversal time scale for almost 200 million years.
Crustal growth rates can be used to calculate estimates for the age of the continental crust. This can be done through analysis of igneous rocks with the same isotopic composition as initial mantle rock. These igneous rocks are dated and assumed to be direct evidence of new continental crust formation. [22]
Oceanic crust is denser than continental crust because it has less silicon and more of the heavier elements than continental crust. [11] [12] As a result of this density difference, oceanic crust generally lies below sea level, while continental crust buoyantly projects above sea level. Average oceanic lithosphere is typically 100 km (62 mi ...
The thickness of Earth's crust (km). The continental crust consists of various layers, with a bulk composition that is intermediate (SiO 2 wt% = 60.6). [5] The average density of the continental crust is about, 2.83 g/cm 3 (0.102 lb/cu in), [6] less dense than the ultramafic material that makes up the mantle, which has a density of around 3.3 g/cm 3 (0.12 lb/cu in).
The team believes, according to Science Alert, that the stretching direction varied by up to 65 degrees, which may have allowed the extensive thinning of the continental crust.
Slab gap hypothesis – Theory in plate tectonics; Slab window – Type of gap in a subducted oceanic plate; Supercontinent – Landmass comprising more than one continental core, or craton; Terrane – Fragment of crust formed on one tectonic plate and accreted to another; Volcano – Rupture in a planet's crust where material escapes
Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium).