Gravity anomalies are areas that have a higher gravitational pull. This can be caused by earthen material of different densities, either lighter or heavier, or by the sheer size of some mountain ranges. The Himalayas are known for this and have such a strong pull they threw off cartographers and surveyors for years. The Appalachian Mountains also have plenty of gravity anomalies, though not to the same extent. These stretch from Georgia to Pennsylvania and are caused by dense accumulations of material or pockets, both formed during the creation of the mountain range.