User:Schnits/geol108

Moai

Nathan Schneider Nas589 245505 Geol 108

Located in the south eastern Pacific Ocean about 3600 kilometres off the coast of Chile is Easter Island. The island is governed by the Chilean government. Easter Island is volcanic in origin, and contains 3 inactive volcanoes, creating an abundance of volcanic, igneous rock. The island had received its name from the Dutch sea captain Jacob Roggeveen who was the first European to visit the island on Easter Sunday of 1722. It has been suggested that the original colonists arrived in only a few canoes and numbered fewer than 100. It is also believed that at the time of their arrival the island was forested and populated with land birds, and was perhaps the most productive breeding site for seabirds in the Polynesia region. The abundance of birds, fish and plant food sources, the colonists settled and the population grew. These people who are known as the Rapanui are rich in religious and artistic culture. This culture produced stone figures, known as the Moai.

What makes these features worth writing about? Why chose them? These stone features are mysterious. They are the topic of a lot of discussion and are a big tourist attraction. Is that why this paper is about them? In the internet comic strip “Red Meat” the character “Papa Moai” is based on these features, and it just happens that it was what I was reading when I decided it was a good time to start on my geology term paper. These figures are on average 14 feet tall and approximately 28,000 pounds, but can be as tall as 172 feet and 300,000 lbs. Of the many figures, Ahu Tahai, was selected to be the subject of this paper. It is the earliest figure on the island, dating back to 690 CE. This particular figure contains 2 types of stone, Tuff for the body of the figure and Scoria, the rock that makes up the Pukao, the stone hat-like object placed on top of the figure. Scoria is a light-weight glassy lava rock. This particular rock is light red in color because of the oxidization of iron found in the rock, although the rock is typically a dark grey or black in color. The rock has a bubbly texture as a result of gasses that escaped during volcanic eruption, most likely a low intensity Strombolian eruption. That also means the original magma had a low viscosity. The tuff for the figure’s body was carved from the slopes of Rano Raraku, one of the three volcanoes found on the island. Rano Raraku is a caldera, a collapsed volcano, which contains high amounts of fine grained volcanic ash. The inside of the quarry contain many Moai, which appear to only be partially done and stuck in a state of being only half formed. After the carvings were freed from the stone, they were moved and placed in various spots on the island. According to legend these stone features actually walked to their locations using spiritual powers, or mana. Tuff has an explosive origin as it is an igneous pyroclastic rock, formed when volcanic ash (Small jagged pieces of rocks, minerals, and volcanic glass less than 2mm in diameter) consolidates.

The Rapanui of Easter Island are rich in culture, and created of many stone figures which are known as the Moai. The Moai are numerous, and diverse, for example Ahu Tahai which contains two types of rock, Tuff and Scoria. Both rocks are volcanic in origin, Scoria one is made from the release of gas in a low intensity volcanic eruption, and the Tuff is formed by the consolidation of glassy, fine grained volcanic ash after an eruption, which is expected considering the island’s volcanic creation.