Wikibooks: Historical Geology/Sea level variations

• Format: Book
• Language: English
• Subjects: Antarc*; Antarctica; Greenland
• Online Access: https://en.wikibooks.org/wiki/Historical_Geology/Sea_level_variations

Changes in global sea level are important both as a symptom and as a cause of [[climate]] change. In this article we shall look at what causes changes in global sea level and how they can be detected in the geological record. =Causes of sea level changes= One cause of sea level variations is the formation or melting of [[continental glaciers]]. It is estimated for example that if the [[ice sheets]] currently covering Greenland and Antarctica were to melt the global sea level would rise by approximately 70 meters. Another factor that affects global sea level is the [[mid ocean ridges]]. The more active they are the larger they are and the more water they displace. The ridges can also change in total length when a [[supercontinent]] rifts apart a [[mid ocean ridge]] will be produced where it rifts the production of the mid Atlantic ridge by the rifting of [[Pangaea]] is the most recent example. As the ridge is in effect a mountain range 40 000 miles long its formation clearly displaced a massive amount of water. [[Hotspots]] producing islands such as Hawaii have a similar though lesser effect. The collision of continents can reduce sea level by reducing the area of the continents as they compress into one another. For example it has been estimated that the collision of India with south Asia and the compression resulting in the raising of the Himalayas would have lowered the sea level by about 10 meters. =Local variations= The position of the shoreline can change as a result of the movement of the land as a result of tectonic events or of [[isostatic rebound]] after depression caused by [[glacial]] cover. This means that there s no use in just looking at one or two places to estimate sea levels in the past because what looks like a global fall in sea levels might in fact be a local rise in the level of the land. Such local effects did in fact confuse the 18 th century scientist Anders Celsius whose measurements of the sea level along the Scandinavian coast convinced him that the seas must be shrinking. He was not ...