Lecture 2 Flashcards
What was the climate during the age of dinos?
1) Continents kept rearranging throughout the time of dinos
2) climate and environmental conditions were very different and varied through time.
How did super continents at the beginning of the time of the dinosaurs have an impact on climate?
The coasts were wet; the interiors were arid (deserts)
The interiors also experienced stronger seasonal temperature swings
What discovery allowed us to see weather from the fossil record?
the foot prints of minisauripus with raindrop impressions
Why is the regulating effect of being near a water body so strong during the time of pangea?
because it was so big
What three pieces of evidence allowed us to see that during the beginning of the time of the dinosaurs
The coasts were wet; the interiors were arid (deserts)
and
The interiors also experienced stronger seasonal temperature swings
desert sands and salt deposits- find desert sands in dry places and salrt deposits formed in lakes and restricted seaways indicating more evaporation occured and left salt crystals than water entered (shows the interiors were arid)
Coals- coals formed in warm wet coastal swamps near the equator, they form when vegetation falls into water and doesn’t break down and then gets buried compressed and heated forming diff types of coal, see these coals in the coasts.
glacial till- we also find glacial till near the south pole which tells us it was once glaciated
As Pangea began to break up what happened to the continents? How did this effect climate?
The continents became smaller, therefore temp swings and aridity in the interior wasn’t that extreme and climates warmed up
Global average temperature was how many degrees warmer than the present?
4-9 degrees warmer.
At the time of the dinosaurs what was the temperature gradient between the equator and poles?
The equator was hot and the poles were cold but the temperature gradient was not at large as the one we see today
Was there permanent ice at the time of the dinosaurs? Was there snow?
there was snow, but no ice at the poles during most of the time of the dinosaurs
The further back you go in the climate record, the less _____ it becomes?
reliable and complete
A 2015 online poll by
YouGov says what percentage of Americans believe humans
and dinosaurs lived at the same time?
41%
What are the two main causes of climate change?
changes in the amount of solar radiation reaching earth
and,
changes in the amount of greenhouse gases in earth’s atmosphere
What are the changes in the amount of solar radiation reaching earth?
there are changes in the sun’s intensity and changes in the distance of the earth from the sun
What are the four main climate archives that allow us to know what ancient climates looked like?
sediment
ice
coral
tree rings
How do the four main climate archives contribute to our knowledge of the climate record?
they preserve continuous records that are datable, they are proxies for climate change as they respond in specific and predictable ways to climatic and environmental changes
What is the principle of uniformitarianism?
That earth is very old and the processes of it have been unform over time, therefore the study of modern geologic processes is useful to understand past geologic events
How do sedimentary rocks serve as evidence for what the climate was like during the mesozoic?
Different rocks form in different environments, sedimentary rocks form in coastal areas with evaporation, swampy areas with plants and cold areas with ice
How do ice serve as evidence for what the climate was like during the mesozoic?
Ice traps atmospheric gases in bubbles. These tell us the concentration of
greenhouse gasses.
The ice record goes back how many years?
2.7 million years
How do tree rings serve as evidence for what the climate was like during the mesozoic?
Seasonal
changes in growth rates
produce bands. The
thickness of the bands
tells you whether climates
were favorable for growth;
the number of bands can
be counted to figure out
how old the tree was
when it died.
Thick bands indicate rainy seasons, thin bands indicate dry seasons
How do fossils serve as evidence for what the climate was like during the mesozoic?
some plants and animals only live in specific habitats, can see fossils in diff environments and ascertain the habitats there
How do isotopes serve as evidence for what the climate was like during the mesozoic?
Fossils and sediments contain isotopes of elements like carbon and oxygen. Animals will
preferentially build their shells out of the lighter isotope, but the ratio of light to
heavy isotope varies with temperature. We can measure the changes in light/heavy
isotope ratios over geologic time to infer how climate changed over time.
Why should we compare between different archives?
because each archive responds differently to change, has variable resolution and provides good records for diff intervals of time
During the time of dinosaurs was temperature relatively warmer or colder? Did it vary from place to place?
warmer, it varied from place to place which shows there was regional climate differences
How is the continuous record of climate change displayed?
Combines climatic changes from different proxies into a single record.
* Results are presented as temperature differences (T) relative to the 1960-
1990 average of around 15°C.
During the time of the dinosaurs CO2 levels were what?
During the entire Time of the Dinosaurs, carbon dioxide levels were 2X to 5X higher
than today, and sometimes even higher (up to 16x).
Where did the greenhouse gases come from during the time of the dinos?
break up of pangea and volcanism
dino gas
Where did the greenhouse gases come from during the time of the dinos in terms of volcanism?
The breakup of Pangea was caused by intense sea-floor spreading, leading to
extensive volcanism.
* Volcanoes release large amounts of greenhouse gases such as carbon dioxide
(CO2) and methane (CH4) into the atmosphere.
Where did the greenhouse gases come from during the time of the dinos in terms of dino gas?
dinos gave off methane through digestion, vast herds of big dinosaurs ate and pooted
How did seal levels fluctuate in the past? What did these changes do?
They fluctuate between low and high, low sea levels made the coastline be between the continental shelf and slope and therefore eroded the shelf, high sea levels rose on top of the shelf (sometimes by 100m) and deposited marine sediments on it
During the time of the dinos were sea levels high or low? How do we know?
high, we find extensive marine deposits
on the continental shelves that
were deposited during the Time of
the Dinosaurs. for ex the white cliffs of dover
What two factors cause sea level rise?
tectonic activity and climatic factors
How does tectonic activity change sea level?
It changes the size of the ocean basin, when it gets smaller sea level will rise cause less space when it gets bigger sea level drop cause more space and an object in it will displace water
How do tectonic plates change the size of the basin?
they collide or separate continents or they change the size of mid ocean ridges for exmaple if they’re colliding they increase the size of ocean so sea level drops but when they split apart the sea level rises cause they’re making the basin narrow.
A fast spearing ridge displaces more water- leads to a higher sea level.
A slow spreading ridge displaces less what, leads to a lower seal level.
Why are mid ocean ridges tall? How tall are they?
they are tall becaus ethey expand due to heating below, the crests of ridges occur On average, the crests of the ridges occur 2500 m below sea level and slope down away
from the crest as the rock cools.
When does a mid ocean ridge rock cool and what depth does it level out at?
The rocks cool completely after ~60 Myr and level out at a depth of ~5500 m below sea
level.
A spreading ridge is ____. A slow spreading ridge is ______.
wider, narrow
How come we don’t know the rates of sea floor spreading more than 100 million years ago?
because part of the record
has been destroyed through
subduction.
If all the ice sheet melted today sea levels would rise by what? what does this tells us about sea level at the time of the dinosaurs?
70 meters, therefore since there was no ice at the time of the dinos sea levels were 70 m higher than today
How did increased temperatures cause raised sea levels at the time of the dinos?
Warm water occupies more space than cool water.
Sea level would have been an additional 7m higher than today (roughly 1 m/ 1
C).
What two other factors outside of plate tectonics and warm temps and sea melt, effect sea levels of the past?
isostasy- the sea floor sags/rebounds in response to changes in the volume of water added/removed, isostacy reduces the effect of adding water by 30%
Variation in the
shape/gradient of the world’s
continental margins
Current estimated indicate that sea levels were how many metres higher towards the end of the time of the dinos?
125 metres
How did high sea levels effect climate?
Flooding of coastal areas had a moderating effect on climate.
the interiors of continents where inland seas developed moderated climate
Towards the end of the time of the dinos decreased volcanism in the sea floor and a drop in sea level caused what?
increased seasonality and increase in temperature gradient between equator and poles.
leading to deterioration of global warm mild climates
