Compared to climate changes due to plate tectonics and astronomical causes, the changes due to volcanic eruptions are:

sudden and quicker

Explanation:

The climate on Earth has always been changing, and there are numerous factors that have had their influence on it. Some of the factors are the plate movement and the astronomical causes. Both of these factors though result in gradual changes of the climate, which can take thousands or even millions of years in order to have a significant change. The volcanic eruptions are another story. They are also one of the factors that influence the climate, but unlike the other two factors that are mentioned, the volcanic eruptions cause sharp and sudden climate changes. If the volcanic eruption is massive, or there are several volcanoes around the world erupting at the same time, they are able to change the global climate in just few days. Usually it is the enormous amounts of ashes and other particles released in the atmosphere that are blocking the sunlight and cause sudden cooling of the planet.