Flu-like Illness. One of the earliest HIV symptoms in men is a severe 'flu-like' illness, known as the 'seroconversion illness.'. Seroconversion is the point in time where a person's blood is converted from being HIV negative to HIV positive, by the production of antibodies.
Erosion causes the surface of mountains to be younger than the rocks that form the mountains themselves. Glacial processes produce characteristic landforms, such as pyramidal peaks, knife-edge arÃªtes, and bowl-shaped cirques that can contain lakes.
Mountains and valleys are created by huge tectonic activity, or movement in the Earth. This movement occurs in many different ways, over millions of years. This lesson will show how mountains and valleys form as the result of tectonic forces.