This is a positive dream. It is a dream of a spiritual awakening and spiritual power.

Most of the dreams that I look at are intended to give the dreamer feedback on how he/she is progressing spiritually and psychologically. Thus, these dreams often contain religious or spiritual symbols. These symbols often come from the depths of the unconscious. This means that these symbols will sometimes have a pagan or mythological appearance. When religious symbols are seen, they are often symbols from Hinduism.

In this particular dream, the active volcanoes are symbolic of an energy called kundalini. When awakened, it rises from the base of the spine to the top of the head. This rising energy is often associated with a feeling of heat along the spine. There can be intense heat at a chakra as it is opened.

The darkness may refer to the darkness at the source of the energy.

The “strange trolley/roller coaster” like ride could be the movement of the energy of kundalini.

Although kundalini is often associated with Hinduism, it is an energy that is within all of us. Most of us do not notice it, because it is “sleeping.”
And for what it’s worth, spontaneous kundalini awakenings are becoming increasingly common.

Hope this helps.