Get your FREE 2-month Skillshare trial: http://skl.sh/minuteearth2 The "Mountain or Valley?" illusion makes our brains turn valleys inside out. But inside-out valleys are a real thing, both on Earth and on Mars. Thanks to Skillshare for sponsoring this video, and to our supporters on https://www.patreon.com/MinuteEarth ___________________________________________ If you want to learn more about this topic, start your googling with these keywords: Inverted relief: a topographic feature, such as an old riverbed, that has reversed its elevation relative to other features. Duricrust: a hard mineral crust formed at or near the surface of soil in semiarid regions by the evaporation of groundwater. Geomorphology: the study of the physical features of the surface of the earth and their relation to its geological structures. Exhumed paleochannel: a remnant of an inactive river or stream channel that has been either filled or buried by younger sediment, and then subsequently uncovered by erosion. Erosion: the action of surface processes, including wind and water, that move dirt and rock from their original location to some other place. Capillary action: the tendency of a liquid in a capillary tube or absorbent material to rise or fall as a result of surface tension. Mineral precipitation: when dissolved compounds in a solution bond together to form a solid (a simple example is how dissolved sodium and chloride ions come together to form salt as water evaporates) ___________________________________________ Credits (and Twitter handles): Script Writers: David Goldenberg (@dgoldenberg) & Emily Elert (@eelert) Video Illustrator: Ever Salazar (@eversalazar) Video Narrator: Emily Elert (@eelert) With Contributions From: Henry Reich, Alex Reich, Kate Yoshida, Emily Elert, Peter Reich Music by: Nathaniel Schroeder: http://www.soundcloud.com/drschroeder Image Credits: Yardangs and Ridges of the Edge of Aeolis Planum - NASA JPL University of Arizona https://hirise.lpl.arizona.edu/PSP_006683_1740 Raised Footprints - Alan Light https://www.flickr.com/photos/alan_light/5904493388/ _________________________________________ Like our videos? Subscribe to MinuteEarth on YouTube: http://goo.gl/EpIDGd Support us on Patreon: https://goo.gl/ZVgLQZ And visit our website: https://www.minuteearth.com/ Also, say hello on: Facebook: http://goo.gl/FpAvo6 Twitter: http://goo.gl/Y1aWVC And download our videos on itunes: https://goo.gl/sfwS6n ___________________________________________ If you liked this week’s video, we think you might also like: The "Mountain Or Valley?" Illusion by MinutePhysics https://www.youtube.com/watch?v=V7C318DGB38 Inverted Relief at Green River, Utah https://www.google.com/maps/@38.8744077,-110.2558884,867m/data=!3m1!1e3 ___________________________________________ References: Clarke, J., July 2016, personal communication. Clarke, J. D., & Stoker, C. R. (2011). Concretions in exhumed and inverted channels near Hanksville Utah: implications for Mars. International Journal of Astrobiology, 10(03), 161-175. doi:10.1017/s1473550411000048 Harris, D.R. (1980). Exhumed paleochannels in the Lower Cretaceous Cedar Mountain formation near Green river. Utah: Brigham Young Univ. Geol. Stud. 27, 51–66. Malin, M. C. (2003). Evidence for Persistent Flow and Aqueous Sedimentation on Early Mars. Science, 302(5652), 1931-1934. doi:10.1126/science.1090544 Miller, R. P. (1937). Drainage Lines in Bas-Relief. The Journal of Geology, 45(4), 432-438. doi:10.1086/624550 Pain, C.P & Ollier, C.D. (1996). Regolith stratigraphy: principles and problems. Journal of Australian Geology & Geophysics, 16(3), 197-202. Pain, C., Clarke, J., & Thomas, M. (2007). Inversion of relief on Mars. Icarus, 190(2), 478-491. doi:10.1016/j.icarus.2007.03.017 Pain, C., July 2016, personal communication.