Like water in the ocean, air in the atmosphere exerts pressure that increases with depth. Most gas molecules in the atmosphere are pulled close to Earth’s surface by gravity. As a result, air pressure decreases quickly at lower altitudes and then more slowly at higher altitudes. This is illustrated in Figure below . Air pressure is greatest at sea level, where the depth of the atmosphere is greatest. At higher altitudes, the pressure is less because the depth of the atmosphere is less. For example, on top of Mount Everest, the tallest mountain on Earth, air pressure is only about one-third of the pressure at sea level. At such high altitudes, low air pressure makes it hard to breathe and is dangerous to human health.
Beth had been practicing for this climb for a long time. She had started out at the base a few days ago and would reach the summit before night.  She had had to slow down as she moved up the mountain because she found it harder to breath but overall it had been a good experience.
is the air pressure higher or lower at the top of the mountain?