FILES OF THE EARTH H ISTORY

Geologists collect and study rocks to find out about the geological history from a part of the earth. Thus if they find granit 400 million years old (m.y.o) in a location, they can state that this region was an active magmatic area during this specific period.
What are some of the most abundant rocks telling us about ancient processes?.
LIMESTONE: a very common sedimentary rock in Spain, specially in the east end north . Places with this kind of rock were once under the sea (not very deep) or they were coral reefs.

Limestone strata

SLATE: metamorphic rock that comes from mudstone when temperature and pressure is high. These mudstones originate from sediments settled on the floor of the ocean, therefore the fossils that we find in the slate come from the fauna who lived over there time ago. Slate in Montes de Toledo has abundant fossils so we can figure out very accurately about the animals existing in the earth oceans 440 million years ago.

fossil "trilobites" on slate

BASALT: rock raised when the volcano lava cools fast. If you find this rock in some place, you can infer that this area was once close to an active volcano.

Every rock has an history. When we put together the histories of different places, we can find out about the big history, THE HISTORY OF OUR PLANET.