Here are today’s questions. Answers will be published on Monday. The theme for this week ran from Mon-Thu; a new theme will come up on Monday.

And the questions follow:

1. What river, known to carry a large load of sediments and possessing one of the largest alluvial fans in the world, broke its banks and shifted course by over 100km in a devastating 2008 flood that displaced over 2.5 million people?
2. Prehistoric volcanoes, followed by sustained erosion over time and channel switching, have led to the Mississippi River shifting its mouth into which water body every thousand years or so?
3. The ancient city of Uruk, described as being ruled by Gilgamesh in the 27th century BC, is believed to have declined in importance due to the change in course of which river?
4. Often called a “war-induced natural disaster”, a 1938 flood was caused by the Yellow River changing its course following the Kuomintang breaking its levees. Almost a million lives are believed to have been lost, but the flood did not stop the Japanese from capturing which city, in the news eight decades later?
5. What river that originates only 240km from the ocean but takes a course over 4,000km long is actually two ancient rivers, that joined together followed stream capture due to erosion?

Here are the answers to 2026: Week 22, Quiz 4:

1. Thales
2. Heron / Hero
3. Median of the triangle
4. Archimedes spiral
5. Theme: Fictional professors
   • Vector
   • Calculus
   • Kelsey ‘Plum’
   • Moriarty