Roca vs. peña vs. peñasco
In Spanish, different words are used to describe the size and type of a rock or boulder. They are 'roca', 'peña', and 'peñasco'. Although they all refer to the same general concept -- a large piece of rock -- they have variations in usage based on the size of the rock and the context in which they are used.
Roca
The word 'roca' is used for rocks in general. It can refer to small, medium, and large size rocks.
La roca en el jardín es muy bonita.
(The rock in the garden is very beautiful.)
Peña
'Peña' usually refers to a larger mass of rock or cliff, often found in mountainous regions.
Subimos la peña para disfrutar de la vista panorámica.
(We climbed the crag to enjoy the panoramic view.)
Peñasco
'Peñasco' is typically used to describe a massive, isolated boulder or crag.
El barco se estrelló contra un peñasco.
(The ship crashed into a massive boulder.)
Summary
While 'roca' generally refers to rocks of any size, 'peña' and 'peñasco' are used for larger formations. 'Peña' refers to substantial rock formations like cliffs, particularly in mountainous areas. On the other hand, 'peñasco' is used for massive, sometimes isolated boulders.