Lesson 9) Statigraphy and Geologic Time

Question 1

Principle of Superposition

Answer 1

Tendency or rock layers to be chronologically stacked.
- Sediments deposited -> gradual build up
- How things normally work, but can be exceptions:.

Question 2

Unconformity

Answer 2

Flat surface caused by partially melted igneous intrusions that are uplifted and eroded

Question 3

Statigraphy

Answer 3

Science of using arrangement and composition of rock layers to interpret geological history

Question 4

Formation

Answer 4

Large uninterrupted sequence of rock that is made of multiple layers that all share similar properties (eg- composition + grain size) all formed under similar conditions

Question 5

What is indicated when a rock changes formations?

Answer 5

Large scale change occurred in the environment where the rocks were deposited.

Question 6

Principle of Superposition

Answer 6

Allows stratigraphies to infer relative age of rock layers (layer age vs other layer age)
- DOES NOT determine absolute age

Question 7

Radiometric dating

Answer 7

Technique to determine rocks age.

As rock ages, isotopes decay and ratio of isotopes : decay product decreases.
Mass spectrometers can measure the isotope ratio of rock, which can tell how old it is.

Question 8

Isotope

Answer 8

Variant of a chemicalelement that has unusual number of neutrons.
- some are unstable and undergo radioactive decay: energy release, resulting in atoms w/ different compositions (decay products)

Question 9

What rock can’t be radiometrically dated?

Answer 9

Sedimentary
They are not new: they are made of sediments that have already formed and are undergoing radioactive decay already probably.

However: can use volvanic ash layers (within sedimentaries to estimate nearby fossil ages)

Question 10

What can usually be radiometrically dated?

Answer 10

Igneous
Formed anew
- When igneous rock solidifies, it starts out w/ isotope ratio equal to that found in its environment

Question 11

How can we measure fossils age, if they’re usually found in sedimentary rocks?

Answer 11

Radiometric dating + principle of superstition

IF found between two horizontally deposited igneous rock layers— can bracket age

Question 12

Geologic Time Scale

Answer 12

Standardized series of chronological divisions that parses Earth’s history into discrete named units.

Eons > Eras > Periods > Epochs

Question 13

Hadean eon

Answer 13

4.4-4 billions yrs ago

Formation and earl Earth years.
- Surface partially molten and hella volcanoes
- Planet collision which formed moon

By then end, Earth had cooled and hella oceans
- organic molecules form

Question 14

Archean Eon

Answer 14

2-2.5 billion yrs ago

• Oldest fossils (single-celled organisms)
• Cynanobacteria made oxygen and stromatolites

Question 15

Stromatolites

Answer 15

Structures formed by cyanobacteria from the Archean Eon
- Lump stones that when cut in half, show layers of secreted sticky limbs trapping sediment particles.

Question 16

Proterozoic Eon

Answer 16

2.5 billion-541 million years ago

• FIrst multicellular organisms
• very poor fossil record as life at this point was BONELESS
  Ediacarian period: Large forms of life (like animals) finally got here bruh

Question 17

Phanerozoic Eon

Answer 17

540-0 millions years ago

Subdivided into 3 eras
- Rapid animal evolution

Question 18

Paleozoic Era

Answer 18

541-252mil years ago

• Primitive ocean-dwelling invertebrates (me fr)
• Big ass forests w/ reptiles, amphibians, insects

Question 19

Cambrian Period

Answer 19

541-485 mil years ago

• Aquatic life diversification (Cambrian explosion)
• Anomacolaris, arthropods, SpongeBob worms etc

Question 20

Ordovician Period

Answer 20

485-443 mil years ago
- OCEAN ANIMALS RULE!!!!

Question 21

Silurian Period

Answer 21

443-419mil years ago
- predator fish get jaws #looksmaxing
- land plants start flourishing
- millipede anthropods start crawling on ocean floor

Question 22

Devonian Period

Answer 22

419-359 mil years ago
- FIrst forests EVOR!!!
- sharks
- the fishies start venturing onto land

Question 23

Carboniferous Period

Answer 23

359-299 mil years ago
- ambhipians swamps and reptiles

Question 24

Permian Period

Answer 24

299-252 mil years ago

• PANGAEA FORMS!!!
• Reptiles evolve into 3 linages which make up every major animal

Question 25

Mesozoic Era

Answer 25

252 - 66 mil years ago
“Age of Dinosaurs”

• Marine reptiles evolve (first true reptiles, mammals, birds)
• First flowering plants

Question 26

Cenozoic Era and its 3 periods

Answer 26

66-0 mil years ago
“Age of Mammals”
- Grass reveal

Periodt!!!
1. Paleocene: 66-23 mil
- Cooling temperatures, mammals + birds diversifying

2. Neogene: 23-2.6mil
- HOMINIDS IN AFRICA

3. Quaternary: 2.6-0 mil
- Ice age
- First anatomically modern humans and civilization

Question 27

Triassic Period

Answer 27

252-201 mil years ago
- Life slowly recovers from mass extinction of Permian era
- first mammals and Dino’s evolve
- Pangaea breaks apart
- Ichthyosaurs + Plesiosaurs = Pterosaurs

Question 28

Dinosaurs of the Triassic Period?

Answer 28

First Ornithischians:
- Pisanosaurus

First Theropods:
- Herrerasaurus
- Eoraptor

First sauropodomporphs:
- Panphagia

Prosaurupods:
- Plateosaurus

Question 29

Ichthyosaurs

Answer 29

“Fish Lizard” but aren’t lizards (nor fish)

Group of reptiles that took on a fish-like lifestyle and evolved a very fish body form (and returning to sea)
- Ancestors: Terrestrial reptiles
- Paddle-like front + hind limbs, fin tail, dorsal fin
- Long snout w/ conical teeth (piscovore)
- BUT: never evolved gills so they still needed to breath air

Question 30

Plesiosaurs

Answer 30

Group of reptiles that a loved secondarily aquatic lifestyle
- Large chests + torsos
- Broad, paddle iambs
- Short tails
- Vary in front

eg) elasmosaurus (keep in mind it lived in Cretaceous period)

Question 31

Pterosaurs

Answer 31

Close relatives of dinosaurs who branched off reptilian family tree at roughly the same time dinosaurs did
- FIRST FLYERS
- Membranous wings supported by elongated

Question 32

Jurassic Period

Answer 32

201-145mil years ago

Dino diversification
- Sauropods were dominant terrestrial herbivores
- small ornithopods
- theropods were dominant terrestrial carnivores
- rhamphorhynchoids and pterodactyloids
- first birds
- first ankylosaurs and ceratopsians (but not diverse yet)

Question 33

Rhamphorhynchoids

Answer 33

Early pterosaurs

eg) stegosaurus

Question 34

Pterodactyloids

Answer 34

Came from ramphorhynchoids, differing in morphology
- short tails
- elongated carpels which made wings longer
- large head crests as display
- ranged in size

eg) pteranodon

Question 35

Early Cretaceous Period

Answer 35

146-100 mil years ago

• first flowers
• spinosaurids and charcharodontosaurids
• coelurosaurian theropods diversify
• iguanodonts get big and many – sauropods decline
• Mosasaurs
• stegosaurs get replaced by ankylosaurs
• primitive birds abundant (better than archaeopteryx)

Question 36

Mosasaurs

Answer 36

Relatives of modern monitor lizards and snakes
- reptiles
- tail finds and paddle limbs
- BUT bodies were longer than ichthyosaurs and plesiosaurs
- most were predatory and big

Question 37

Late Cretaceous Period

Answer 37

100-65 mil years ago
- all the famous celebrity Dino’s
- coelurosaurian theropods abundant and diverse
- ankylosaurs diverge into two: ankylosaurids and clubless nodosaurids
- Ceratopsians and hadrosaurs are dominant herbivores (northern)
- titanosaurid sauropods are dominant herbivores (southern)
- pachycephalosaurs!!!
- flower plants evolve <3
- THEN THEY ALL DIE!!!! MASS EXTINCTION!!!!!

Question 38

What were some coelurosaurian theropods that lived

Answer 38

Tyrannosaurs, oviraptorosaurs, dromaeosaurids, oviraptosaurs, therizinosaurs, troodontids

Question 39

How long ago was the Earth formed?

Answer 39

4.6 billion years ago