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

Earth l Earth facts, pictures and information. Earth is the third planet from the Sun and the fifth largest: Planet Profile orbit: 149,600,000 km (1.00 AU) from Sundiameter: 12,756.3 kmmass: 5.972e24 kg History of Earth Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet. Earth, of course, can be studied without the aid of spacecraft. The Earth is divided into several layers which have distinct chemical and seismic properties (depths in km): 0- 40 Crust 40- 400 Upper mantle 400- 650 Transition region 650-2700 Lower mantle 2700-2890 D'' layer 2890-5150 Outer core 5150-6378 Inner core The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. atmosphere = 0.0000051 oceans = 0.0014 crust = 0.026 mantle = 4.043 outer core = 1.835 inner core = 0.09675 Earth's Satellite Open Issues

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. The magnetosphere is the region above the ionosphere and extends several tens of thousands of kilometers into space, protecting the Earth from cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation. Importance[edit] Humans have used compasses for direction finding since the 11th century A.D. and for navigation since the 12th century.[10] Although the North Magnetic Pole does shift with time, this wandering is slow enough that a simple compass remains useful for navigation.

Swarm reveals Earth’s changing magnetism -- ScienceDaily 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. The latest measurements also confirm the movement of magnetic North towards Siberia. These changes are based on the magnetic signals stemming from Earth's core. This will provide new insight into many natural processes, from those occurring deep inside our planet to space weather triggered by solar activity.