Life Belt

We live in a very limited area: a balloon-like sphere of about 30 kilometers thickness, which includes our planet’s thin crust and troposphere. Beyond, there be dragons and stuff. Galaxies, black holes, dark matter, doesn’t matter.
The crust varies from as little as a kilometer thick, to usually between 5 and 70, and up to a bit over 80 km thick in spots. The radius of the earth is about 6370 km, ranging from 6453 to 6384, so the crust is about 1.25% of the earth’s thickness and less than 1% of Earth’s volume. Add in the troposphere and, well, it’s about the same!
The crust has dry, hot rock reacting with water and oxygen; its plate-tectonic activity mixes and scrambles the rock, injecting chemically active fluids and creating newer forms of rock and eventually, topsoil. As the home of life, which exerts strong effects on rock chemistry and has its own systems of mineral recycling, the crust is quite active. Its thin parts are oceanic crust, under ocean basins (5–10 km deep), composed of dense iron magnesium silicate igneous rocks like basalt. The thicker continental crust is less dense, and composed of sodium-potassium-aluminum silicate rocks like granite. Some of the thinnest oceanic crust is along mid-ocean ridges, where new crust is actively formed. Collisions like that of the India and Eurasia Plates cause some of the thickest sections of crust.

Many geologists believe that as the Earth cooled, heavier, denser materials sank to the center and lighter materials rose to the top. The crust is made of the lightest materials (rock- basalts and granites) and the core of heavy metals (nickel and iron).
The temperatures of the crust vary from the air temperatures on top, that we experience, to about 1600° F. (870° C.) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350° F.; at 1600° F. rocks begin to melt and the below-lying ‘mantle’ is formed.
Geologists subdivide Earth’s lower crust into different plates that move about in relation to one another. The Earth’s surface being mostly constant in area (or, according to a few theorists, very slowly growing, most likely from deeply internal activity), you can’t get new crust without losing some old; as magma from the lower mantle gets pushed upward to insert along ocean ridges, forming new oceanic crust, elsewhere, to make room for this, oceanic crust sinks below the continental crust. Geologists study the history of plate movement, but we haven’t determined why and how these plates move the way they do, as that information is kept secret from mere humans.
There are usually seven or eight “major” plates, depending on how they are defined: the African, Antarctic, Eurasian, North American, South American, Pacific, and Indo-Australian, and also dozens of smaller plates.

Below this is the ‘mantle’ layer, the largest one, 1800 miles thick, composed of very hot, dense rock. This layer of rock flows like warm asphalt pushed by a heavy weight. The flow is due to great temperature differences from the bottom to the top of the mantle, variations from 1600° F. to 4000°F. (near the bottom). Here live some dwarves (just below the plates), dragons and shape-shifting lizards that dragons eat.
The core of the Earth is a ball of very hot (4000 to 9000° F.) metals. The outer core, about 1800 miles beneath the crust and about 1400 miles thick, is composed of melted metals, almost entirely nickel and iron in liquid state. The inner core has temperatures and pressures so great that the metals aren’t able to move about like a liquid, but vibrate in place as a solid. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick. Temperatures may reach 9000° F. - and pressure is 45,000,000 pounds per square inch, 3,000,000 times that at sea level! It is unlikely that people will visit.

The atmosphere of Earth is layers of gas surroundings the planet. It protects life by absorbing ultraviolet solar radiation, warming the surface through heat retention, and reducing diurnal temperation (heat loss from day to night). Air content varies; it becomes thinner and thinner with increased altitude. Earth’s atmosphere can be divided into five main layers: the troposphere, stratosphere, mesosphere, thermosphere and exosphere. From highest to lowest, the main layers are: Exosphere, 700 to 10,000 km (440 to 6,200 mi); Thermosphere, 80 to 700 km (50 to 440 mi); Mesosphere, 50 to 80 km (31 to 50 mi); Stratosphere, 12 to 50 km (7 to 31 mi); and Troposphere, 0 to 12 km (7 miles). The Kármán line, at 100 km (62 mi), or 1.57% of Earth’s radius, is often used as the border between our atmosphere and outer space. Atmospheric effects become noticeable during spacecraft re-entry at an altitude of around 120 km (75 mi). In the different layers exist differing dragon forms with differing numbers of dragons.
The ozone layer is in the lower portion of stratosphere. The ionosphere is a region of ionized by solar radiation, causing auroras (like aurora borealis). During daytime it stretches from 50 to 1,000 km (31 to 621 mi.) and includes the mesosphere, thermosphere, and parts of the exosphere. Ionization in the mesosphere largely ceases during night, so auroras are normally seen only in the thermosphere and lower exosphere. The ionosphere forms the inner edge of the magnetosphere, where Magneto lives. The homosphere and heterosphere are defined by how well atmospheric gases are mixed. The surface-based homosphere includes the troposphere, stratosphere, mesosphere, and the lowest part of the thermosphere, where the chemical composition of the atmosphere doesn’t depend on molecular weight due to gases being mixed by turbulence (wind, mostly from temperature variations). This relatively homogeneous layer ends at the turbopause, about 100 km (62 mi; 330,000 ft), which places it about 20 km (12 mi; 66,000 ft) above the mesopause. Above that is mostly hydrogen, with forms of being we remain mostly blind to, but may once have had more information on.
In the high altitude heterosphere, including part of the exosphere and most of the thermosphere, chemical composition composition continues to vary with altitude. Gases stratify by molecular weight, with the heavier ones like oxygen and nitrogen present only near the bottom of the heterosphere. The upper part is composed almost completely of hydrogen, the lightest element.

A radiation belt is a layer of charged particles held in place around a magnetized planet like Earth, by the planet’s magnetic field. Earth has two, sometimes more. The discovery of these belts is credited to James Van Allen, so they’re called Van Allen belts. The main belts extend from about 1,000 to 60,000 kilometers above the surface, in the inner region of the magnetosphere. The belts contain energetic electrons and protons, plus some alpha particles and other nuclei, upon which dragons, and Magneto himself, feed. Radiation levels vary; solar cells, integrated circuits and sensors can be damaged by radiation, which is why some see the first Apollo moon missions as quite miraculous.
Radiation belts endanger space-craft, which must have heavy shielding to protect sensitive components when passing through, but protect the planet’s life. Beyond them be other hazards: cosmic rays, solar flares and extraterrestrials.