Mountain
Heights of mountains are typically measured above sea level. Using this metric, Mount Everest is the highest mountain on Earth, at . There are at least 100 mountains with heights of over above sea level, all of which are located in central and southern Asia. The highest mountains above sea level are generally not the highest above the surrounding terrain. There is no precise definition of surrounding base, but Denali, Mount Kilimanjaro and Nanga Parbat are possible candidates for the tallest mountain on land by this measure. The bases of mountain islands are below sea level, and given this consideration Mauna Kea ( above sea level) is the world's tallest mountain and volcano, rising about from the Pacific Ocean floor.
Mount Jefferson (Oregon)
The second tallest mountain in the U.S. state of Oregon after Mount Hood, Mount Jefferson lies within Jefferson, Linn, and Marion counties, in the central part of the state. Reaching an elevation of , the volcano has a proximal relief of . It is not usually visible from the city of Portland or other places within the Willamette Valley region, though it can be noticed from highways to both the east and the west of the Cascade Range. The average elevation of the terrain around Jefferson is , meaning that Jefferson's cone rises nearly above its surroundings.