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The exact upper and lower boundaries of the mesosphere vary with latitude and with season (higher in winter and at the tropics, lower in summer and at the poles), but the lower boundary is usually located at altitudes from 47 to 51 km (29 to 32 mi; 154,000 to 167,000 ft) above sea level, and the upper boundary (the mesopause) is usually from 85 ...
The upper boundary is defined by the sharp increase in seismic wave velocities and density at a depth of 660 kilometers (410 mi). [8] At a depth of 660 km, ringwoodite (γ-(Mg,Fe) 2 SiO 4) decomposes into Mg-Si perovskite and magnesiowüstite. [8] This reaction marks the boundary between the upper mantle and lower mantle. This measurement is ...
Location of Mesoamerica in the Americas: this prototypic culture area is situated on the Middle American isthmus, or land bridge, adjoining southern North America with South America. The geography of Mesoamerica describes the geographic features of Mesoamerica , a culture area in the Americas inhabited by complex indigenous pre-Columbian ...
Below are separate lists of countries and dependencies with their land boundaries, and lists of which countries and dependencies border oceans and major seas. The first short section describes the borders or edges of continents and oceans/major seas. Disputed areas are not considered.
Mesoamerica and its cultural areas. Mesoamerica is a historical region and cultural area that begins in the southern part of North America and extends to the Pacific coast of Central America, thus comprising the lands of central and southern Mexico, all of Belize, Guatemala, El Salvador, and parts of Honduras, Nicaragua and Costa Rica.
Antarctica Map of island countries: these states are not located on any continent-sized landmass, but they are usually grouped geographically with a neighbouring continent. Determining the boundaries between the continents is generally a matter of geographical convention. Several slightly different conventions are in use.
A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of the Earth. While this is true of any map, these distortions reach extremes in a world map.
The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure. Earth's inner structure can be described both chemically ( crust , mantle , and core ) and mechanically.