it is active

The Nevado del Ruiz eruption of 1985 was one of the most destructive eruptions in history. Part of its aftermath was the largest lahar in geological history, bringing the fatality total to over 23,000 people.

Initially, the volcano began spewing large amounts of sulfur dioxide, which is extremely detrimental to humans. It causes violent coughing and wheezing shortly after being inhaled, and has a very strong, putrid smell. The main problem, however, was that sulfur dioxide can easily chemically react with various substances to form dangerous products, such as sulfuric acid.

The volcano then began to experience strong seismic activity, leading up to the eruption. After the eruption, the physical structure of the Nevado del Ruiz, (stratovolcano) led to the corroding of a nearby lake and the creation of a lahar. Measurments leading up to the eruption indicate that the pH level of the lake was around .2, meaning that the sulfur dioxide was already reacting with the lake water to form an acidic solution.

Lahars are syrupy in substance, in a liquid state while in motion and solid when stopped, very similar to concrete. The Nevado del Ruiz lahar became a worldwide phenomenon due to the death toll it created and the Omayra Sanchez incident.

it is a stratovolcano, if u are talking about its shape. basically, it is cone shaped. if this is not what u were talking about, then i am sorry...