Chapter 9 Flashcards
1
Q
What is the principle of Superposition
A
-the tendency for rock layers to be chronologically stacked
- there are exceptions
- > as igneous rocks that form from volcanic activity can vertically cut through horizontally arranged layers of locks
- > mountains building events may tilt, fold and even flip rock layers
2
Q
What is stratigtaphy
A
-it is the science of using the arrangement and composition of rock layers to interpret geological history
3
Q
What is a formation
A
- A LARGE UNINTERRUPTED SEQUENCE OF ROCK THAT IS made up of multiple layers
- > these layers all share similar properties
- > properties include mineral composition and average sediment grain size
-note these sequences of rock formed under similar conditions
4
Q
What does a changing formation indicate
A
-that a large scale change occurred in the environment where the rocks were being deposited
5
Q
Does the principle of superposition allow to determine the absolute age of the rocks
A
- no
- > it allows to determine the relative age
- > that is how old one layer is in relative to another
6
Q
How do you age rocks in absolute terms
A
- by using a technique called radiometric dating
- > all matter is composed of chemical elements
- > some of these chemical elements may exist as isotopes
- some isotopes are unstable and will undergo radioactive decay
- > where the energy is released and a new atom with a different compositon of particles results
- > these resulting atoms with different particle compositions are called the decay products
- > when a new rock forms, it has a ratio of isotopes and decay products that matches the environment
- using a mass spectrometer, it is possible to measure the isotope ratio of a rock
- > this ratio can tell you how long ago the rock formed
7
Q
Can sedimentary rocks be radiometrically dated
A
- no
- >because they are made of sediments that had already been undergoing radioactive decay
8
Q
Can igneous rocks be radiometrically dated
A
- yes
- >because they are formed anew
9
Q
How can you tell the age of fossils
A
- by combining radiometric dating and the principle of superposition
- if sedimentary rocks that contain fossils are horizontally deposited between two igneous rocks
- > then the dating of the igneous rocks above the sedimentary layers will tell us what the age of fossils must be older than
- > dating the igneous rocks below the sedimentary layer will tell us what the age of the fossils are younger than
-so this process gives an overall bracket of the age of fossils
10
Q
What is the geologic time scale
A
- it is a standardized series of chronological divisions that brings together the Earth’s history into discrete named units
- > the largest units in the time scale are Eons
- > followed by Eras, Periods and Epochs
11
Q
Describe the Haden Eon
A
- it was from 4.6 billion to 4 billion years ago
- by the beginning of this eon, the rest of the unverse was already over nine billion years old
- the surface of the Earth at this time was partially molten and with volcanic activity widespread
- at roughly 4.5 billion years ago, the Earth collided with another planetoid
- > this collision ejected a large mass of debris
- > which was held in Earth’s orbit and eventually became the moon
- by the end of this eon
- > the earth had cooled and the oceans covered most of the surface
-note the oldest rocks on earth have been dated at only about 4.4 billion years old
12
Q
Describe the Archean eon(4 to 2.5 billion years ago)
A
- the oldest fossils come from the Archaean eon
- these fossils are simple single-celled organisms
- > more advanced forms later evolved, including cyanobacteria
- cyanobacteria were photosynthetic and eventually produced a large amount of oxygen gas
- > this gas became concentrated in the Earth’s atmosphere
- some cyanobacteria formed stromalites
- > which look like lumpy stones
- > but when you cut them in half, you see the layers that were created as the cyanobacteria secreted sticky films that trapped particles of sediment
13
Q
Describe the Proterozoic eon
A
- 5 billion to 541 million years ago
- at approximately 1.7 billion years, the first multicellular organisms evolved
- the time span from 630 to 542 million years ago is known as the Ediacaran period
- >during this time, large forms of life with some harder parts evolved, including the fist animal life
14
Q
Describe the Phanerozoic eon
A
541 to 0 million years ago
- it is subdivived into three eras
- > these eras are subdivided into numerous periods
- it is during this time that animal life rapidly evolved into multitude of diverse forms
- > including dinosaurs
15
Q
Describe the Palezoic era
A
541 million to 252 million years ago
- at the start of this ear
- > animal life was restricted to primitive invertebrates living in the oceans
- > great forests covered the land and teamed with reptiles, amphibians and insects
16
Q
Describe the Cambrian Period
A
541 to 485 million years ago
- it marks the beginning of the dramatic diversification of aquatic animal life
- > referred to as the Cambrian explosion
- > sponges, molluscs, worms and many kind of anthropods evolved at this time
17
Q
Did Anomalocaris, Opabinia and Pikaia come from the Cambrian Period
A
-yes
18
Q
Describe the Ordovician Period
A
- it occured from 485 to 443 million years ago
- global sea levels were high
- life in the oceans continued to diversify
- > with fish increasingly becoming the dominant large aquatic animals
19
Q
Describe the Silurian Period
A
- it occurred from 443 to 419 million years ago
- until this point, fish had not yet evolved jaws
- with the evolution of jaws, came large predatory fish
- primitive plant life began to flourish on land
20
Q
Describe the Carbineferous Period
A
- 359 to 299 million years ago
- amphibians were widespread in the abundant swamps
- reptiles, the first amniotes evolved
- much of the coal that is mined today is formed from the rotting plants of Carbiniferous swamps
21
Q
Describe the Permina Period
A
- continents collided together and formed a single super continent called Pangeea
- reptiled involved into three main lineages
- > anapsids(would become turtles)
- > synapsids(go on to evolve mammals)
- > diapsids(evolve into lizards, snakes, crocodiles and dinosaurs)
- many of the terrestrial rocks from this period of time represent dry, desert environments
22
Q
Describe the Mesozoic Era
A
- 252 million to 66 million years ago
- referred to as the age of dinosaurs
- ,any kind of marine reptiles evolve, including the ichthyousars, plesiosaurs and mosasaurs
- the first flowering plants evolved towards the end of the Mesozoic
23
Q
Describe the Cenozoic Era
A
- it is 66 to 0 million years ago
- it is often referred to as the age of mammals
- the extinction of dinosaurs allowed mammals to evolve into large forms
- > note mammals had been around since the Triassic
24
Q
Describe the Paleogene Period
A
- 66 to 23 million years ago
- global temperatures began to cool
- mammals diversified into a variety of new forms
- > including primates, bats and whales
- > birds also diversified
25
Describe the Neogene Period
- 23 to 2.6 million years ago
- global temperatures continued to cool
- the first hominids evolved in Africa
26
Describe the Quaternary Period
- 2.6 million to 0 million years ago
- the earth experienced several large events, such as the ice age
- humans first evolved
27
When did the Triassic Period begin
- from 252 to 201 million years ago
- during the first ten million years of the Triassic, life gradually recovered from the mass extinction that occured at the end of the Permian
- the first mammals and dinosaurs evolved during the later portion of the Triassic
- >so did the first pterosaurs(first vertebrates to fly)
- Pangaea began to break apart
28
Do many dinosaurs from the Triassic period look similar
- yes
- the first representatives
- >the ornithiscians, theropods and sauropodomorphs were all mostly small and bipedal
29
Did the ichthyosaurs evolved during the Triassic
- yes
- >their name means fish lizard
- >they are a group fo reptiles that took on a fish-like lifestyle
- their ancestors were terrestrial reptiles
- >but found success by making an evolutionary return to the water
- they had paddle like front and hind limbs
- >a finned tail and a shark-like dorsal fin
- >their long snouts resembled those of dolphins and were filled with conical teeth
- >they did not have giills and needed to come to the surface to breath
30
Did the plesiosaurs evolve during the Triassic period
- yes
- >they had large chests and torsos
- >broad paddle-shaped limbs
- >and relatively short tails
- in front of their shoulders, there was huge variation
- >some had short necks and huge jaws
- >others had elongated necks and small heads
31
Did the pterosaurs evolved during the Triassic
- yes
- >they are commonly called pterodactyls
- >they are closer relatives of dinosaurs who branched off from the reptilian family tree at roughly the same time in the Triassic that dinosaurs did
- they were the first vertebrates to fly
- they have membranous wings supported by a single extremely elongated finger
32
Which group did eary pterosaurs belong to
- they belonged to a group called rhamphorhybchoids
| - >that were common in the Late Triassic and throughout the Jurassic
33
Was Jurassic Period the peak of sauropod diversity
- yes
- Jurassic period was from 201 to 145 million years
- >sauropods were very diverse and the dominant terrestrial herbivores
34
Describe the general characteristic of organisms that formed during the Jurassic
- ornithopods were common
- non-coelurosaurian theropods(Allosaurus) were dominant terrestrial carnivores
- the stegosaurs are almost completely restricted to the Jurassic
- the first ankylosaurs, ornithopods and ceratopsians appear at this time
- >but they are not very abundant or diverse
-the first birds, including Archaeopteryx evolved ruing the Jurassic
35
What happened to rhamphorhynchoid pretosaurs during the Jurassic
- they gave rise to a new pterosaur group
| - >called the pterodactyloids
