EARTH'S SURFACE

Rotorua Morning Post, Volume 2, Issue 519, 1 May 1933, Page 2

EARTH'S SURFACE

NOT SO RUGGED AS IS GENiERALLY THOUGHT. SOME COMPARISONS. It is not generally realised that the irregularities of the earth's surface are infinitestimal compared with the size of .the globe. The popular impression that the earth's crust is very rugged has been "heightened," so to speak, during the last week by the success of British airmen in flying for the first time over Mount Everest — the world's highest peak. Much has been heaxd also in recent weeks of the ocean deeps, in relation to the Pacific earthquake zone. If it were possihle to stand oif in | space, and literally "view the world in proper perspective," our old globe would appear almost perfectly smooth. Mount Everest is 29,000 odd feet in height. The greatest ocean depth — the Tongan Deep, off the island of Tonga. — is about 31,000 feet. This gives us a distance of 60,000 feet, roughly 12 miles, hetween the two extremes, or amout on-three hundred and thirtieth of the earth's radius (the diameter of the earth heing ahout 8000 miles). Tiny Cut. Now, if you had a globe 330 feet in diameter, representing the earth, the distance hetween the top of Mount Everest and the deepest known ocean could he shown by a cut of only six inch.es on the surface of the sphere. Let us put it another way. On a sphere the height of a man — say ahout six feet — a scratch merely one-tenth of an inch deep would suffice to represent to scale the maximum amount of irregularity on the earth's crust. So far we have been talking only of the differenee between extremes, or maximum height and depth. A Mere Yarnish. If we take the average elevation of the earth's surface ahove sea level, which is 230 feet, and the average depth of the ocean helow sea level, which' is 12,500 feet, we have a total of 14,800 feet, roughly three miles, or ahout one-thirteen hundredth of the i earth's radius. To realise how very smooth the earth's surface is it is only necessary to be told by geologists that it would not be possihle to represent the average undulation on an ordinary glohe as used for deriionstration purposes in the schools. It would not he more than the coating of varnish on such' a globe!