Petroleum was formed on the ground → under
many millions of years ago. Plants and
animals live in the sea sank to the seabed → living
when they died. Their remains mixed with
sand and mud in layered deposits, built up
slowly over the years. A combined action of → The
heat, pressure and bacteria turned these
deposits into petroleum. The petroleum
moved slowly upwards to the porous rocks or
became trapped there. With the passage of
time, land what was once under water rose to → that
the face of the sea. As such, petroleum → surface
deposits are now found on or near dry land.