Formation of mountains –weathering, erosian.

Sedimentary rocks

Dating RocksRelative - Absolute

Nicolai Stenonis (1638-1686). "...at the time when any given stratum was being

formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being

formed, none of the upper strata existed.”

Steno’s Principle of Superposition

(Prodromus, 1669)

That is, in a sequence of strata, any stratum is younger than the sequence of strata on

which it rests, and is older than the strata that rest upon

it.”

Radioactive element Half-life

Radon-219 4 seconds

Iodine-131 8 days

Cobalt-60 5 years

Caesium-137 30 years

Carbon-14 5,730 years

Uranium 238 700 million years

Potassium-40 1.25 billion years

Radioactive Isotope Decays to Half-life (years)

Rubidium-87 Strontium-87 49,000,000,000

Rhenium-187 Osmium-187 41,600,000,000

Thorium-232 Lead-208 14,000,000,000

Uranium-238 Lead-206 4,500,000,000

Potassium-40 Argon-40 1,250,000,000

Uranium-235 Lead-207 704,000,000

Samarium-147 Neodymium-143 108,000,000

Iodine-129 Xenon-129 17,000,000

Aluminium-26 Magnesium-26 740,000

Carbon-14 Nitrogen-14 5,730

1 proton = neutron + electron.

An atom nucleus looses an electron:1 Neutron 1 proton.

( atom number +1, atom mass not changed)

An atom nucleus gains an electron:1 proton 1 neutron.

( atom number -1, atom mass not changed)

e = N-P; gains a N, loses a P

Radioactive Isotope Decays to Half-life (years)

Rubidium-87 Strontium-87 49,000,000,000

Rhenium-187 Osmium-187 41,600,000,000

Thorium-232 Lead-208 14,000,000,000

Uranium-238 Lead-206 4,500,000,000

Potassium-40 Argon-40 1,250,000,000

Uranium-235 Lead-207 704,000,000

Samarium-147 Neodymium-143 108,000,000

Iodine-129 Xenon-129 17,000,000

Aluminium-26 Magnesium-26 740,000

Carbon-14 Nitrogen-14 5,730

Accuracy of Radiometric Dating.

1. Several radioisotopes usually occur together in a rock and decay at different rates so the dates can be cross-checked. Nevertheless, invariably the dates agree.

Accuracy of Radiometric Dating.

2. The half-life of isotopes doesn’t change when scientists subject them to extreme temperatures and pressures or chemical environments.

Radiometric dating of meteorites:

the earth and solar system are 4.6 billion years old.

(Oldest earth rocks - Northern Canada:4.3 billion years old)

N gains 1 e (e = N-P)

Accuracy of Radiometric Dating.

1. Several radioisotopes usually occur together in a rock and decay at different rates so the dates can be cross-checked. Nevertheless, invariably the dates agree.

Accuracy of Radiometric Dating.

2. The half-life of isotopes doesn’t change when scientists subject them to extreme temperatures and pressures or chemical environments.

Accuracy of Radiometric Dating.

3. Radiometric dates coincide with dates obtained by other methods.c) Carbon dating agrees with the

historic record.d) Dates of the early paleozoic

coincide with dates calculated from annual and daily coral rings.

e) Radiometric dates agree with dates obtained from tree rings.

The Fossil Record

Fossils:= Remains of past organisms.

Actual (or petrified) body (parts) Excrements (coprolites) Gastroliths (stomach stones) Imprints (burrows, foot, feathers ) molecular residues

Coprolites.

Fossilization:1. Remains in water (river, lake, ocean)2. Sink to the bottom.3. Get covered by sediment

Fossils in sedimentary rock! Exceptions:a) tar pits (La Brea, Los Angeles)b) conifer amberc) sanddunes

TIME

Fossilization

Xing Xu stands among the remains of duck-billed dinosaurs in Zhucheng, China

Nature 6 September 2012 vol 489 p22

Fossilization:1. Remains in water (river, lake, ocean)2. Sink to the bottom.3. Get covered by sediment4. Petrified

Hard > soft body parts Aquatic > terrestrial

5. Discovery of fossils Exposure on the surface Timely removal

The fossil record must be incomplete

Fossil plant, Carboniferous

Turtle sex recorded in rock.

Jeholodens: early mammaliformes

(165 million years old)

Nature 1999, 398, p326.

Jeholodens jenkinsi

(165 million years ago)

Eomaia: common ancestor of the Eutheria or placentals.

(About 128 million years old)

Nature 2002, 416 p816.

Eomaia: common ancestor of the Eutheria or placentals.

(About 128 million years old)

Nature 2002, 416 p816.

Eomaia: common ancestor of the Eutheria or placentals.

(About 128 million years old)

Nature 2002, 416 p816.

Jeholornis: long-tailed, seed-eating bird of the early cretaceous of China.

(Nature 2002, 418 p405).

What does the fossil record tell?

1. The history of life on earth is old.

3.5 bya: first life

Stromatolites(2 .7 billion years ago)

What does the fossil record tell?1. History of Life: old2. Fossils are lacking in the oldest

layers. 3.5 bya: first life (bacteria) 1.5 bya: eukaryotes 0.7 bya: multicellular organisms 0.45 bya:fish 0.35 bya: amphibians 0.30 bya: reptiles 0.20 bya: mammals 0.15 bya: birds

TrilobitesOrdovician, Oklahoma

The fossilized remains of a pregnant mare and fetus (white circle) offer a glimpse into the reproduction of E. messelensis.

American Association for the Advancement of Science Science 2014;346:792-793

Published by AAAS

Archaeopteryx:A transitional fossil between reptiles & birds

Intermediate forms

Thick, bony wall around middle ear.

Large, powerful tail, shorter legs, fat pad in jaw for hearing, brakish water

Salt water habitat

Nasal opening shifted back, eyes on side of head

Tail flukes, very small hindlegs,

Echolocation for hunting

Complete loss of hind legs, nasal opening reaches position of blowhole

in living whales

Baleen for filtering food

Hippopotamus

(Pakicetus)

(Ambulocetus)

(Kutchicetus)

(Rodhocetus)

(Dorudon)

(Basilosaurus)

Reconstruction of the Tethys Sea in the Middle Miocene (45 Mya)

What does the fossil record tell?

1. History of Life: old.2. Fossils are lacking in the oldest

layers.3. Earliest life simpler ; more

recent organisms more comlex.4. Many extinct organisms.

Ordovician

What does the fossil record tell?

5. Ancient organisms were very different from living species, resembling modern species more and more as one moves up to more recently formed rocks.

What does the fossil record tell?

6. Fossils in adjacent layers above and below) were more similar to each other than to those found in layers more widely separated.

Crinoids

What does the fossil record tell?

7. Fossils in the most recently deposited rocks tend to resemble modern species living in THAT area.

Fossil marsupials were found in profusion only in recent sedimentary rocks of Australia, and that is where most modern (extant) marsupials live.

Thylacoleo carnifex (marsupial lion)

What does the fossil record tell?

8. There are no authentically anachronistic fossils!.

Island Biogeography

Biogeography:= Distribution of life on earth.

Islands:

Continental IslandsEngland (0.3 Mya), Japan, Sri Lanka, Madagascar (160 Mya)

Oceanic Islands: Hawaii, St. Helena, Juan

Fernandez, Galapagos

Hawaii

Galapagos

Juan Fernandez Archipelago

St Helena

Juan Fernandez Archipelago

Juan Fernandez Firecrown

Masafuera Ravadito

Marine Inguano

Hawaiian Islands

Hawaiian monk seal

St. Helena Wirebird (Charadrius sanctaehelenae)

St. Helena Wirebird (Charadrius sanctaehelenae)

Three facts about oceanic islands:

1. They are missing groups of species that live on continents and continental islands

2. The groups that ARE found on oceanic islands are replete with many similar species.

3. Often related, but not identical, to species living on nearby continents.

Compared to other areas of the world, life on oceanic islands is

UNBALANCED.

Native Missing

some Plants Land mammals

some Birds Reptiles

some Insects Amphibians

Freshwater fish

Good Colonizers

The End.