Isotopes in Fossil Dating

Isotopes and Fossil Records

• Fossil records contain FscopSs, which are familiar to animals using isotopes to build drips and shallower rates to change with temperature.
• This helps to reconstruct past climate changes by analyzing the isotopes' ratings.
• Temple's width during time was several wommer, and the still vertab rates went down from place to place.

Climate Change and Sea Levels

• Carbon dioxide levels won't stay the same and will change the climate, which affects sea levels.
• During the time of the dinosaurs, the sea level was higher due to high temperatures.
• Even a 1% change in sea levels would contribute to the sea levels rising, which affected the climate.

Continental Movement and Volcanic Activity

• Pangea, a supercontinent, broke apart due to volcanic activity, which led to the formation of new oceans.
• This volcanic activity caused an increase in global temperatures, contributing to climate change.
• The breaking apart of Pangea also led to the formation of different continents, which in turn affected sea levels.

Mid-Ocean Ridges and Sea Floor Spreading

• Mid-ocean ridges are areas where new oceanic crust is being created due to volcanic activity.
• This process leads to the expansion of the ocean floor and the movement of continents.
• The ocean floor spreading is a slow process that has been occurring over millions of years.

Sea Level Changes and Ice Ages

• Changes in sea levels are due to the movement of continents and the changing volume of water in the oceans.
• During ice ages, sea levels were lower due to the ice caps locking away water, and when the ice melted, sea levels rose.
• Changes in sea levels have been occurring over millions of years, affecting the Earth's climate.

Continental Collisions and Sea Level

• Continent-continent collisions pile continents on top of each other, creating larger ocean basins and causing sea level to drop.
• During the time of Pangaea, sea level would have dropped due to continental collisions.
• Splitting the continents apart would have kept sea level higher than it is today.

Mid-Ocean Ridges and Sea Level

• Mid-ocean ridges at divergent boundaries are tall due to heating from below, causing them to expand.
• The crests of the ridges occur 2500 m below sea level and slope down away from the crest as the rock cools.
• The rocks cool completely after ~60 Myr and level out at a depth of ~5500 m below sea level.
• Fast-spreading ridges are wider than slow-spreading ridges due to the rate of cooling.
• When rates of spreading are higher, more water is displaced by the ridges than when rates are slower.

Climatic Factors and Sea Level

• If all the ice sheets melted today, sea level would rise almost 70 m.
• Ice sheets were not present during the Time of the Dinosaurs, therefore sea level was almost 70 m higher.
• Warm water occupies more space than cool water, resulting in a 7m higher sea level than today (roughly 1 m/ 1°C).

Other Adjustments to Sea Level

• Isostasy reduces the effect of adding a large volume of water by ~30%.
• Variations in the shape/gradient of the world's continental margins also affect sea level.

Cretaceous Sea Levels

• Current estimates indicate that towards the end of the Time of the Dinosaurs, sea levels were ~125 m higher than today.
• However, the reasons are not fully understood.

Summary

• Climates were warmer during the time of the dinosaurs.
• Fast spreading resulted in more volcanism.
• Giant, gassy dinosaurs existed.
• Sea levels were higher due to warmer climates, melting of ice sheets, and thermal expansion of water.
• Faster rates of spreading ripped continents apart, reducing the size of ocean basins.
• Mid-ocean ridges took up more space.
• Flooding of coastal areas had a moderating effect on climate.
• Decreased volcanism on the sea floor and a drop in sea level caused increased seasonality and a greater temperature gradient between the equator and poles.