What are hyaloclastites?

Answer 1

A rocktype formed by the flowing or intrusion of lava or magma into water, ice, or water-saturated sediment, and its granulation or shattering into small angular fragments. The process is often driven by contact steam explosivity, cooling processes or mass movement. The sediment consists of hyaline shards of rapid solidified magma and volcanic clasts which are bound together with a glassy or feltlike matrix with the same composition as the clast. They are observed at all types of submarine volcanism (like mid-ocean ridges or seamounts).