Half a mile up the track that runs past our house there's a small quarry, mostly mined for its rock to be crushed down as aggregate for use in maintaining the estate roads. A closer look at the rock shows that....
....it is formed of particles of previous rocks varying in size from cobbles down to finely-crushed grains. Normally, if the larger particles are fairly rounded, the rock is termed a conglomerate; if the particles are angular, it's a breccia.
An even closer look shows that there is considerable variety in the constituent rocks. This would normally suggest that, whatever mechanism(s) produced the rock derived it from an extensive area. So, for example, the rock might have been formed as a beach, with the materials brought from miles away by the sea or by nearby rivers.
My knowledge of geology is rusty from the years of neglect in favour of other interests such as archaeology, but I feel that this rock was formed rapidly, but not so rapidly that the agent moving the material didn't have time to round some of the larger particles and sort the different grades. So the agent of erosion might have been a river, though a river might have sorted the particles more than is seen here.
What I do feel about this rock is that it was formed quickly and violently.
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