Lecture 27
No description yet. This curated deck is ready for daily study.
Card preview (24)
What was caused by the Grenville orogeny?
heat loss by reflective land mass causing 3 periods of glaciation the Sturtian, Marinoan, and Gaskers
When was multicellular life found and what was it?
Since about 630 million years ago, with the Ediacaran fauna, which was Earth’s 1st major radiation of multicellular life, although enigmatic. The oldest macroscopic fossils of soft-bodied organisms, phylogenetic relationship uncertain, and the accumulation of sufficient free O2.
What was the Cambrian explosion?
538 million years ago, the oldest fossils of the ancestors of all living organisms that are alive today suddenly and explosively appeared and radiated the Earth
What is phylum?
The taxonomic group that includes organisms that share similar characteristics such as mollusca, arthropoda, porifera, cnidaria, annelida, and chaetognatha
When was New England founded and how?
The accretion was 440 million years ago, where the taconic orogeny (mountain building event happened)
During the taconic orogeny what was the US like?
The continent was mostly underwater, where shallow marine limestone (sedimentary rock) was formed, and in deeper sea shale (sedimentary rock) was formed, but there was no plate boundary nearby NE US was a passive margin
What happened about 440 million years ago?
the development of a subduction zone with an accompanying volcanic chain was formed causing marine sediment limestone and shale to be crushed between the two land masses and become metamorphosed as NA and this volcanic chain collide
The metamorphosed limestone and shale became?
inwood marble and manhattan schist
Remnants of the taconic orogeny can be found?
in the Taconic Mts, where the marine sediments were crushed, metamorphosed, and thrust westward and up
What did the Acadian orogeny cause?
Avalonia, a large land mass, to approach the North American plate, affecting a much larger area on the east coast of the US forming the appalachian Mountains
Following the Acadian orogeny what was formed?
The supercontinent Pangea
What happened during the Mesozoic era?
The break up of Pangea and the beginning of rifting as NE USA is under an extensional stress breaking apart from Africa to form the Atlantic ocean
What is PETM?
Paleocene-Eocene Themal Meximum, 55 million years ago 5-10K gigatons of carbon were released into the ocean and atmosphere in less than 10000 years causing average global temp to rise by 5-9 degrees C in 15-20K
PETM was the ________ in the last 65 million years
warmest
The Pleistocene glaciation did what?
Began about 2.6 million years ago, covering 1/3 of Earth’s land mass in ice sheets, lowering sea level by 130 m of present day, and NYC was played under about a 2 mile thick ice sheet
What did the glaciation period do?
It led to glacial deposits at the terminal moraine = southernmost extent of the ice sheet and to the north leaving outwash sand and gravels forming long island
What is an ice age?
A long interval of time (millions to tens of millions of years) when global temperatures are relatively cold. They have glacial and interglacial periods
What theory explains why glacial periods come and go?
The Milankovitch theory/cycle, where the key is the expansion of glaciers beyond a threshold.
The Albedo effect is a
positive feedback loop
What is the albedo (reflectivity) effect?
light-colored surfaces are more reflective and thus have a higher albedo than dark surfaces, which absorb more sunlight
What are the key things to look at to determine when glacial periods come and go?
How much sun light the northern hemisphere receives during the summer because it controls how much ice can melt in the summer, and the amount of sunlight received by the Earth changes periodically based on the orbit and rotation of the Earth
What are the three ways in which the amount of sunlight received by Earth can vary over time?
How much the earth is tilted relative to the Sun, whether the Earth wobbles a lot of a little as it spins on its axis, and the shape of Earth’s orbit as it goes around the sun
What is obliquity?
The Angle of tilt
Tilt angle varies from ______
about 21.5-24.5 degrees over about 41000 years.