Why is there no sea floor that is older than about 250 million years?

The oldest oceanic crust is about 260 million years old it is due to the process of subduction ,oceanic crust tends to get colder and denser with age as it spread off the mid ocean ridges . It gets so dense that it sinks in the upper mantle (subduction).

While winters are rainy, summers are dry. regions with this climate are usually in the eastern part of the continents. they experience hot, humid summers and colder winters. precipitations have a regular distribution throughout the year, but hurricanes are common.

The peak above is part of the  sierra madre occidentals ,  a chain of volcanic mountains that runs through the middle of central america.