The surface area of the Earth is 510,069,262 sq. km. or 5.101 x 108 sq. km. The area of lithosphere is 1.408 x 108 sq. km. and that of hydrosphere is 3.704 x 108 sq. km. In other words, the lithosphere occupies roughly 29.2% and hydrosphere 70.8% of the earth's surface. If we consider the Earth to be a sphere of 30.5cm diameter, the highest mountain peak will be within one mm. height and the deepest point of the ocean within one mm. depth of this sphere. It is, therefore, clear that man's knowledge of the Earth is very limited and indirect.
The Composition of the Earth's Crust. Experiments have proven that 98% of the crust is composed of 8 elements and the rest of the 90 elements compose the remaining 2% of the crust. Even in the 2% portion, only one dozen elements predominate.
The major elements of the Earth's crust (percentage)
Serial No. Elements Percentage
1. Oxygen 46.60
2. Silicon 27.72
3. Aluminium 8.13
4. Iron 5.00
5. Calcium 3.63
6. Sodium 2.83
7. Potassium 2.59
8. Magnesium 2.09
98.59
"The world is a book, and those who do not travel read only a page", St. Augustine said. Here at www.travel-university.org we believe that every page must be read and explored. Travel is an avenue of learning that no text or classroom can teach. The world is a living classroom and you the student. We invite you to the www.travel-university.org library where you can read general interest and detail oriented articles.
