| MadSci Network: Earth Sciences |
Hello,
Ok, here is my lengthy reply to your question...let's see if I can cover all the bases... :)
The earth is made up of five parts, or layers so to speak.
The atmosphere is the gaseous envelope that surrounds the solid body of the planet. Although it has a thickness of more than 1100 km (more than 700 mi), about half its mass is concentrated in the lower 5.6 km (3.5 mi). The gases within it are mostly Nitrogen and Oxygen, which we breathe. I calculated the volume of the air to be approximately :
volume = 7.081 x10^20 cubic meters
assuming an average density of 1.2 kg/m3 which
decreases as we increase altitude
mass = 8.497 x10^20 kg = 0.014% of earth's mass
38% of earth's volume
The lithosphere, consisting mainly of the cold, rigid, rocky crust of the
earth extends to depths of 100 km (60 mi). The rocks of the lithosphere have an
average density of 2.7 g/cm3 and are almost entirely made up of 11 elements,
which together account for about 99.5 percent of its mass. The most abundant is
oxygen (about 46.60 percent of the total), followed by silicon (about 27.72
percent), aluminum (8.13 percent), iron (5.0 percent), calcium (3.63 percent),
sodium (2.83 percent), potassium (2.59 percent), magnesium (2.09 percent) and
titanium, hydrogen, and phosphorus (totaling less than 1 percent). In addition,
11 other elements are present in trace amounts of 0.1 to 0.02 percent. These
elements, in order of abundance, are carbon, manganese, sulfur, barium,
chlorine, chromium, fluorine, zirconium, nickel, strontium, and vanadium. The
elements are present in the lithosphere almost entirely in the form of
compounds rather than in their free state. These compounds exist almost
entirely in the crystalline state, so they are, by definition, minerals.
The lithosphere comprises two shells :the crust and upper mantle that are divided into a dozen or so rigid tectonic plates. The crust itself is divided in two. The sialic or upper crust, of which the continents consist, is made up of igneous and sedimentary rocks whose average chemical composition is similar to that of granite and whose density is about 2.7 g/cm3. The simatic or lower crust, which forms the floors of the ocean basins, is made of darker, heavier igneous rocks such as gabbro and basalt, with an average density of about 3. Taking all of this and some other factors into consideration, we get:
volume = 5.054 x10^19 cubic meters
density of 2.7 g/cm3
mass = 1.365 x10^23 kg = 2.18 % of earth's mass
= 2.72 % of earth's volume
The mantle extends from the base of the crust to a depth of about 2900 km
(1800 mi). Except for the zone known as the asthenosphere, it is solid, and its
density, increasing with depth, ranges from 3.3 to 6 g/cm3. The upper mantle is
composed of iron and magnesium silicates. The lower part may consist of a
mixture of oxides of magnesium, silicon, and iron.This layer is made up of
mostly 11 elements : oxygen, silicon, aluminum, iron, calcium, sodium,
potassium, magnesium, titanium, hydrogen, and phosphorous. These 11 elements
are all mixed up within different compounds in a crystal form, so that we can
call them minerals. For this layer we calculate a value of:
volume = 9.199 x10^20 cubic meters
density ranges from 3.3 g/cm3 (upper mantle) to
6.0 g/cm3 (lower mantle)
mass = 4.278 x10^24 kg = 68.4 % of earth's mass
= 49.5 % of earth's volume
The Hydrosphere is the layer of water which covers about 71% of the
earth's surface. This layer is the combination of rivers, seas, lakes,
underground water, and all the world's oceans. The average depth of the
oceans is 3794 m (12,447 ft), more than five times the average height of the
continents. The mass of the oceans is approximately 1.35 quintillion (1.35 ×
10^18) metric tons, or about 1/4400 of the total mass of the earth. This is
0.04 % of the earth's mass.
The Core is the center part of the earth and is actually divided into an outer core and inner core. Seismological research has shown that the core has an outer shell about 2225 km (1380 mi) thick with an average density of 10 g/cm3. This shell is probably rigid, and studies show that its outer surface has depressions and peaks, the latter forming where warm material rises. From this we can calculate :
volume = 1.719 x10^20 cubic meters
density of 10 g/cm3
mass = 1.719 x10^24 kg = 27.5 % of earth's mass
= 9.25 % of earth's volume
In contrast, the inner core, which has a radius of about 1275 km (795
mi), is solid. Both core layers are thought to consist largely of iron, with a
small percentage of nickel and other elements. Temperatures in the inner core
may be as high as 6650°C (12,000°F), and the average density is estimated to be
13 g/cm3. Phew!!! The values we can determine for the inner core are :
volume = 8.939 x10^18 cubic meters
density of 13 g/cm3
mass = 1.162 x10^23 kg = 1.86 % of earth's mass
= 0.48 % of earth's volume
The entire earth weighs 6 thousand, billion, billion tons!!!
I hope this helped you out...thank you for the question...
Tye Morancy
"Mad Scientist"
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