The color of the Aurora depends on the altitude and the atom being struck by solar radiation (causing excitation). At higher altitudes, there is more Atomic Oxygen than Nitrogen, leading to the common color stratifications you see.
500-200 km altitude
— Atomic Oxygen — Red
— Atomic Oxygen — Greenish-Yellow
— Ionized Nitrogen — Blue/Purple
— Nitrogen (N2) — Crimson
Oxygen only emits red at higher altitudes because once it’s excited, it takes a longer time to emit red than it does green. Why is that important? Well, at lower altitudes there is more Nitrogen for the Oxygen to bump into and absorb that excitation-energy before it gets a chance to emit red light. In this case, where the collision occurs, the Oxygen will emit Green and at low enough altitudes the Nitrogen-Oxygen collisions eventually prevent Oxygen from emitting any light at all.
During stronger storms, high energy solar particles will reach lower in the atmosphere and cause the Crimson emission from Nitrogen, creating a deep-red band at the lower edge of the aurora. Other elements emit light too, like Hydrogen (Blue) or Helium (Purple) which are at higher altitudes.
Mount Nyiragongo is a stratovolcano in the Virunga Mountains associated with the Albertine Rift. It is located inside Virunga National Park in the Democratic Republic of the Congo. The main crater is about two km wide and usually contains a lava lake. The crater presently has two distinct cooled lava benches within the crater walls - one at about 3175m (10,400 ft) and a lower one at about 2975 m (9800 ft). Nyiragongo’s lava lake has at times been the most voluminous known lava lake in recent history. Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa’s historical volcanic eruptions.
Space Shuttle Columbia
Volcano Creates New Island South of Japan
A volcanic eruption has raised an island in the seas to the far south of Tokyo, the Japanese coast guard and earthquake experts say.
Advisories from the coast guard and the Japan Meteorological Agency say the islet is about 200 meters (660 feet) in diameter. It is just off the coast of Nishinoshima, a small, uninhabited island in the Ogasawara chain, which is also known as the Bonin Islands.
Read more: http://www.laboratoryequipment.com/news/2013/11/volcano-creates-new-island-south-japan
Credit: Karl Tate, via SPACE.com
If you don’t love whales you are wrong