Lunar Impact Processes
Section M.4.1.
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Introduction to Lunar Craters

One of the Moon's most prominant landforms are craters. Craters are given different names to indicate their type and size. For example, walled plains are 60 to 300 km wide and have crater walls that are massive and disturbed by other smaller craters, landslides and valleys. Ring mountains are summetrical craters that have a diameter of 20 to 100 km and have close quarters, terraced inner slopes and circular walls with well defined summits. In addition, these craters also have landslides on the crater walls.

Craters with flooded floors that are 5 to 200 km wide are flooded by lava because of the craters original formation or by a volcano forming inside of a crater and flooding this crater with lava.

Those with the width of 5 to 60 km are just called craters. They have a relatively sharp rim, a circular wall, and no central peak.

Finally, the smallest craters that can be seen from earth are called crater pits or craterlets, for their small size, 5 km or less, have the same description as craters.

The nearside had 300,000 craters larger than 1 km and 234 crater bigger that 100 km; this is perfect for finding rare minerals on the Moon that the Moon has none by itself.

The largest craters, on the nearside, filled with lava from the Moon's interior 3 billion years ago, and are now called maria.

-- Marvin Ostrega

Lunar Impact Processes

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