The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust).
The problem behind your itchy skin might be insufficient vitamin intake. There are a number of vitamins that promote the hydration and healthiness of your skin. A shortage in these could trigger itchiness, dry skin and other skin conditions. Alternatively, an overdose of such vitamins might also lead to itchy skin.
Your doctor also may want to evaluate your itchy upper back to rule out internal disease. Liver disease, celiac disease, iron deficiency and thyroid issues may cause itchy skin on the back, according to MayoClinic.com. Treatments If itchy upper-back skin is caused by dry skin, moisturize the skin daily. Use moisturizer after getting out of the bath or shower to lock moisture in place. Taking an oral antihistamine and applying corticosteroid cream to skin on the upper back can reduce inflammation and itchiness, according to MayoClinic.com.