background preloader

Plate tectonics

Plate tectonics
The tectonic plates of the world were mapped in the second half of the 20th century. Remnants of the Farallon Plate, deep in Earth's mantle. It is thought that much of the plate initially went under North America (particularly the western United States and southwest Canada) at a very shallow angle, creating much of the mountainous terrain in the area (particularly the southern Rocky Mountains). Plate tectonics (from the Late Latin tectonicus, from the Greek: τεκτονικός "pertaining to building") is a scientific theory that describes the large-scale motion of Earth's lithosphere. This theoretical model builds on the concept of continental drift which was developed during the first few decades of the 20th century. The geoscientific community accepted the theory after the concepts of seafloor spreading were later developed in the late 1950s and early 1960s. Key principles The outer layers of the Earth are divided into the lithosphere and asthenosphere. Types of plate boundaries

Related:  Mesoproterozoic era

Grenville orogeny Extent (orange regions) of the Grenville orogeny, after Tollo et al. (2004) and Darabi (2004). Timescale[edit] The problem of timing the Grenville Orogeny is an area of some contention today. The timescale outlined in Toby Rivers’ recent work[2] is derived from the well-preserved Grenville Province, and represents one of the most detailed records of the orogeny. Structure of the Earth Structure of the Earth Assumptions[edit] The force exerted by Earth's gravity can be used to calculate its mass, and by estimating the volume of the Earth, its average density can be calculated. Astronomers can also calculate Earth's mass from its orbit and effects on nearby planetary bodies. Structure[edit] Earth's radial density distribution according to the preliminary reference earth model (PREM).[1]

Earth l Earth facts, pictures and information. Terra, Sol III Earth is the third planet from the Sun and the fifth largest: orbit: 149,600,000 km (1.00 AU) from Sun diameter: 12,756.3 km mass: 5.972e24 kg Stromatolite Morphology[edit] Fossil record[edit] Archean[edit] Some Archean rock formations show macroscopic similarity to modern microbial structures, leading to the inference that these structures represent evidence of ancient life; namely stromatolites. However others regard these patterns as having been due to natural material deposition or other mechanism, and thus abiogenic. Scientists have argued for origin due to stromatolites because of the presence of organic globule clusters within the thin layers of the stromatolites, and of aragonite nanocrystals (both features of current stromatolites),[3] and because of the persistence of an inferred biological signal through changing environmental circumstances.[4][5]

Rock cycle Historical development[edit] The original concept of the rock cycle is usually attributed to James Hutton, from the eighteenth century Father of Geology. The rock cycle was a part of Hutton's uniformitarianism and his famous quote: no vestige of a beginning, and no prospect of an end, applied in particular to the rock cycle and the envisioned cyclical nature of geologic processes. Earth's magnetic field Computer simulation of the Earth's field in a period of normal polarity between reversals.[1] The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core.[2] The North Magnetic Pole wanders sufficiently slowly to keep ordinary compasses useful for navigation.

Sediment Sediment billowing out from Italy's shore into the Adriatic Sea Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice, and/or by the force of gravity acting on the particle itself. Sediments are most often transported by water (fluvial processes), wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Rock (geology) Rocks have been used by mankind throughout history. From the Stone Age rocks have been used for tools. The minerals and metals we find in rocks have been essential to human civilization.[1] Three major groups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology.

Swarm reveals Earth’s changing magnetism The first set of high-resolution results from ESA's three-satellite Swarm constellation reveals the most recent changes in the magnetic field that protects our planet. Launched in November 2013, Swarm is providing unprecedented insights into the complex workings of Earth's magnetic field, which safeguards us from the bombarding cosmic radiation and charged particles. Measurements made over the past six months confirm the general trend of the field's weakening, with the most dramatic declines over the Western Hemisphere. But in other areas, such as the southern Indian Ocean, the magnetic field has strengthened since January. Mesoproterozoic This era is marked by the further development of continental plates and plate tectonics. The first large-scale mountain building episode, the Grenville Orogeny, for which extensive evidence still survives, happened in this period. This era was the high point of the Stromatolites before they declined in the Neoproterozoic.