Moons of our Solar System
Moons of our Solar System

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Moons of our Solar System

2.9 Crater morphologies

Now explore these final cross-sectional shapes (morphologies) typical of craters of different sizes, and learn about some of the reasons why morphology depends on size.

Figure 26 Bowl-shaped craters
  • A – Smallest crater type.
  • B – Depth typically 20% of crater diameter.
  • C – Concave crater floors; made up of rocks melted during the impact and fractured pieces of solid rock.
  • D – Ground beneath the crater floor is heavily fractured due to impact.
  • E – Crater rim is built up by layers of material ejected as the crater formed.
Figure 27 Flat-floor craters
  • A – More mature simple craters.
  • B – Like bowl-shaped craters, but material from crater walls slumps down into the crater, making the floor much flatter.
Figure 28 Central-peak craters
  • A – Smallest of the complex crater morphologies.
  • B – Generally flat crater floors, made up of significantly greater proportions of impact-melted rock compared to simple craters, with a peak or cluster of peaks in the centre.
  • C – Peak forms when underlying material rebounds after crater formation, pushing upwards and rising above the crater floor.
Figure 29 Peak-ring craters.
  • A – Similar to central-peak craters, but the central peak here rebounds and rises so much that it becomes unstable.
  • B – To regain stability, the oversized central peak collapses in on itself, leaving behind a ring of uplifted material surrounding a flat area in the centre.
Figure 30 Multi-ring basin craters.
  • A – The largest craters, associated with only the largest impactors and most energetic impacts. 
  • B – Crater diameters are so large that they contain several concentric rings of uplifted material, i.e. a larger version of peak-ring craters.
  • C – In multi-ring basins, the largest proportion of material excavated by the impact event is melted, pooling in the centre of the basin floor.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371