The most difficult Earth riddles A list of Earth related questions that are most often answered incorrectly Geology quiz What is the most common element (by mass) forming the planet Earth?Iron is most abundant in the Earth's outer and inner core, and it is the fourth most common element in the Earth's crust.very hard 31% carboncarbon27%oxygenoxygen19%ironiron31%siliconsilicon20%Created by: globalquiz.org. Statistics based on 5981 answers in 2 languages »elements riddles » If Earth's radius was larger by 1 meter, how much longer would its equator be?By approx 6 meters. For each circle, the length of the circumference is c=2πr. Hence, if a radius grows by 1 meter, the circumference grows by 2 π meters - no matter what the initial value of radius was.hard 43% by approx 6 metersby approx 6 meters43%by approx 6 kilometersby approx 6 kilometers17%by approx 60 kilometersby approx 60 kilometers21%by approx 6000 kilometersby approx 6000 kilometers17%Created by: SpikeMe. Statistics based on 13546 answers in 2 languages »math riddles » In which month is the Earth closest to the Sun?In January. Earth's perihelion occurs around January 3, and the aphelion around July 4. The distance change is about 3.5%, which gives 6.9% increase in solar energy reaching the Earth at perihelion relative to aphelion. Since the southern hemisphere is tilted toward the perihelion, the southern hemisphere receives more energy from the Sun than does the northern over the course of a year. hard 46% in Januaryin January46%in Marchin March6%in Junein June31%there is no differencethere is no difference14%Created by: globalquiz.org. Statistics based on 8812 answers in 4 languages »Sun riddles » After what is the Jurassic period named?A mountain range in Switzerland. The Jurassic period is named for the Jura Mountains in between France and Switzerland, where many fossils have been found.hard 50% a type of ancient lizarda type of ancient lizard12%a mountain range in Switzerlanda mountain range in Switzerland50%a type of coal formed in that perioda type of coal formed in that period15%Latin for 'before mammals'Latin for 'before mammals'22%Created by: Roy Zhu. Statistics based on 7105 answers in 2 languages »Switzerland riddles » What part of the Earth's surface is dry land?29,2%. It is currenlty 29.2% - but it may decrease in the near future due to global warming and sea level rise.hard 56% 29,2%29,2%56%33,6%33,6%26%38,4%38,4%10%42,1%42,1%6%Created by: Krzysztof Moskal. Statistics based on 3700 answers in 2 languages »water riddles » Why is the ozone hole dangerous?It increases UV radiation. In the ozone layer, ozone molecules absorb UV-B and UV-C radiation - short wavelength forms of ultraviolet that can disrupt organic molecules, producing cancerous changes in living cells.easy 70% it speeds up the global warmingit speeds up the global warming21%it increases UV radiationit increases UV radiation70%it depletes the oxygen (O2)it depletes the oxygen (O2)5%it disturbs Earth's magnetic fieldit disturbs Earth's magnetic field3%Created by: Riho Ishii. Statistics based on 7048 answers in 4 languages »ecology riddles » Play geology quiz and see all the questions.