10 most difficult geology riddles

The Richat Structure in Mauritania, also known as the Eye of the Sahara, was interpreted as an asteroid impact structure, but no evidence of shock metamorphism has been found. Today, scientists believe that it is a huge (40 km in diameter) and deeply eroded geologic dome.

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.

Sable Island is believed to have formed from a terminal moraine deposited on the continental shelf near the end of the last Ice Age. It emerges from vast shoals and shallows which, in tandem with frequent fog and sudden storms, have caused over 350 recorded shipwrecks

Gunung Mulu national park is located in the eastern province of Sarawak, Malaysia. It is located on Borneo, near the southern border of Brunei. Gunung Mulu National Park has the largest known natural chamber or room – Sarawak Chamber. It is 700 m (2,300 ft)) long, 396 m (1,299 ft) wide and at least 70 m (230 ft) high

The Baltic Sea is one of the largest brackish inland seas by area, and occupies a basin formed by glacial erosion during the last few ice ages. It is about 1,600 km (990 mi) long, an average of 193 km (120 mi) wide, and an average of 55 metres (180 ft) deep. The maximum depth is 459 m (1,506 ft).The current course of the shoreline was formed about 2 thousand years ago.

Blue amber is a rare variety of amber. It has only been found in the Dominican Republic. Under artificial light, the amber appears like ordinary amber, but under sunlight it has an intense fluorescent blue glow. Blue amber emits a very agreeable smell, which is different from regular amber. There are several theories about the origin of Dominican blue amber, there is a great probability that it owes its existence to ingredients such as anthracene as a result of 'incomplete combustion' due to forest fires among the extinct species Hymenaea protera trees about 25 to 40 million years ago.

The Book of Caverns is an important Ancient Egyptian netherworld book of the New Kingdom. Like all other netherworld books, it is also attested on the inside of kings’ tombs for the benefit of the deceased. It describes the journey of the sun god Ra through the six caverns of the underworld, focusing on the interaction between the sun god and the inhabitants of the netherworld, including rewards for the righteous and punishments for the enemies of the worldly order, those who fail their judgment in the afterlife.

Mount Augustus is located in the Mount Augustus National Park in Western Australia. Mt Augustus is widely claimed in tourist promotional and information literature as the "world's largest monolith" but the claim does not originate from the geological literature, nor is substantiated by any other scholarly research. Mt. Augustus is more than twice the size of Uluru. Unlike Uluru, which is a monolith and, in general, devoid of plant growth, Mt. Augustus is a monocline.

El Totumo Mud Volcano is an active mud volcano located near sea level in northern Colombia in the municipality of Santa Catalina. Situated beside a lagoon and 15m (49ft) high, it is a local tourist attraction.

Tombolos are formed by wave refraction. As the waves near an island, they are slowed by the shallow water surrounding it. These waves then refract or "bend" around the island to the opposite side as they approach, sweeping sediment together from both sides.