The definition of acidic lava is molten material flowing from a volcanic vent. Characteristics of acidic lava is that it is viscous, high in silicates (minerals) and doesn't flow very far. The lava that is more common flows very quickly and does not have as thick of a texture and acidic lava is usually associated with composite cone volcanoes and the basic lava is usually associated with shield volcanoes.
Overcrowding and slums developed in many impoverished countries in the 20th century, mostly due to large migrations to cities from people looking for work.
