What occurs to the altimeter when the static port is blocked?

When the static port is blocked, the altimeter will continue to display the last altitude reading it had before the blockage occurred, effectively "freezing" at that value. This happens because the altimeter relies on the ambient static pressure outside the aircraft to determine the altitude. If the static port becomes obstructed, the altimeter is unable to sense changes in external air pressure, which is necessary for it to provide accurate altitude information.

As the aircraft climbs or descends, the ambient pressure changes, and the altimeter needs to sense these changes to adjust its reading. With a blocked static port, these changes cannot be detected, so the altimeter will not reflect the actual altitude and will instead hold on to the last known pressure reading. This can lead to significant navigational issues if the pilot is not aware of the blockage.