EARTH’S History Part one 8. E EARTH’S History Part one 8.E.2 Understand the history of Earth and its life forms based on evidence of change recorded in fossil records and landforms. 8.E.2.1 Infer the age of Earth and relative age of rocks and fossils from index fossils and ordering of rock layers (relative dating and radioactive dating).

What are fossils? https://www.youtube.com/watch?v=Nbt x9MQx-ac A fossil is the preserved remains or traces of an organism that lived in the past. fossils provide important evidence of how life and environmental conditions have changed.

How are earth processes today compared to earth processes of the past? The earth processes we see today, including erosion, movement of lithospheric plates, and changes in atmospheric composition, are similar to those that occurred in the past.

Water, wind, glaciers, and gravity all can change the land through the processes of erosion.

Earth’s atmosphere has changed over time The early atmosphere held barely a trace of oxygen. By 2.7 billion years ago, a new kind of life had established itself: photosynthetic microbes called cyanobacteria, which were capable of using the Sun'­s energy to convert carbon dioxide and water into food with oxygen gas as a waste product The rise of oxygen occurred slowly, over hundreds of millions of years enabling subsequent, more complex forms of life to thrive

Some of the factors that have changed the composition of Earth’s atmosphere include:

The surface of the Earth has changed over time due to the movement of lithospheric plates The Early Earth and Plate Tectonics https://www.youtube.com/watch?v=QDqskltCixA

What are other events that have changed Earth’s past? Earth’s history is also influenced by occasional catastrophes, such as the impact of an asteroid or comet.

Can Earth be hit by objects out in space? About once every 10,000 years something very large hits the Earth. There are many objects out there that could potentially hit the Earth and do a lot of damage. These are PHOs. They may be comets (PHCs) or asteroids (PHAs).

Who is responsible for monitoring potentially dangerous objects in space? It is thought that to be potentially dangerous an object must be at least 150m in diameter and pass within 46 million miles of Earth. NASA, at present, has identified just over 1000 objects like these and are keeping a close eye on them.

How do comets, asteroids, and meteors differ?

The Barringer crater –a mile-wide Crater that was Created by a 130 foot meteor in Arizona.

This is the location of the impact that is thought to have caused the extinction of the dinosaurs 65 million years ago.

How are fossils important in helping us learn about the history of the earth? Fossils give clues to the diversity of living things over the history of Earth, give clues to past climate and surface changes on Earth, and give clues to changes that have occurred with organisms over time.

We can learn about the past by studying fossils. Knowing the formation process of mold, cast, petrified, preserved, carbonized, and trace fossils also helps us understand earth history The formation process of fossils varies depending on where and under what environmental conditions they formed.

Fossils are only formed in sedimentary rock.

The different types of fossils include: Fossil types The different types of fossils include: Preserved fossil Mold fossil Cast fossil Petrified fossil Carbonized fossil Trace fossil

Mold fossils https://www.youtube.com/watch?v=G4jM2t3NHPA Mold fossil – forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.

Cast fossils Cast fossil – forms when a mold is filled with sand or mud that hardens into the shape of the organism.

Petrified fossils Petrified fossil -form when minerals replace all or part of an organism. Water is full of dissolved minerals. It seeps through the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind. Over time, these deposits completely replace the remains, forming an image of the bones out of solid rock.

Preserved fossils Preserved fossil – forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.

Preserved fossils--- How can an organism be preserved in amber? Sometimes these organisms were trapped in the sap or resin that seeped out of trees. These organisms could be as big as lizards or as small as very tiny gnats. Fossils in amber are one of the few ways that organisms are preserved without a change in form.

Preserved fossils---How are fossils preserved in ice? Freezing -This is the best means of preservation of ancient materials. It happens only rarely. The animal must be continually frozen from the time of death until discovery. That limits the possibilities to cold hardy animals from the last ice age. There have been remarkable discoveries of mammoth and wooly rhinoceros found in ice from Alaska and Siberia. Specimens with flesh, skin, and hair intact have been found. Some of these finds suggest that they were flash frozen, with food still in the mouth and stomach.

Otzi the Iceman is a well- preserved natural mummy of a man from about 5300 BP. The mummy was found in 1991 in the Schnalstal glacier in the Otztal Alps, on the border between Austria and Italy. He is Europe's oldest natural human mummy, and has offered an unprecedented view of Chalcolithic (Copper Age) Europeans.

Ötzi – the Iceman https://www.youtube.com/watch?v=WA3AiNup7fY The body and his belongings are displayed in the South Tyrol Museum of Archaeology in Bolzano, northern Italy.

Preservation in volcanic ash https://www. youtube. com/watch On a fateful summer morning in A.D. 79 Mount Vesuvius buried the vibrant Roman city of Pompeii—and many of its citizens—beneath tons of volcanic ash and debris. The ruined city remained frozen in time until it was discovered by a surveying engineer in 1748.

Preserved fossils- have also been created by peat bogs, paraffin deposits, and volcanic ash https://www.youtube.com/watch?v=1ySRAJY92wE 2000 years ago the Celts and their kin believed the bogs of Northern Europe were entrance to the realm of the gods. Bogs are filled with a natural embalming fluid, acidic water, low in oxygen and rich with tannins (the same chemicals used to cure leather). Over time dead vegetation turns into peat, harvested for heating fuel.

Pictures of Bogs

Preserved fossils---How can fossils be preserved in tar or asphalt? Asphalt- In what is now downtown Los Angeles lies a 23 acre park called The La Brea Tar Pits, officially Hancock Park. Within the park are over 100 pits filled with sticky asphalt or tar. The tar pits were formed by crude oil seeping through fissures in the earth. The lighter elements of the oil evaporate leaving thick sticky asphalt. The pits are famous for the number and high quality of Pleistocene fossils that have been pulled from the pits. The fossils date between 10 and 40 thousand years old. Asphalt is an excellent preservative. Bones, teeth, shells, the exoskeletons of insects, and even some plant seeds have been pulled from the pits. And of course many saber tooth cats.

La Brea Tar https://www. youtube. com/watch La Brea Tar https://www.youtube.com/watch?v=nBfMa62fkHA Tar pit in Los Angeles, California Fossils from the tar pits were "re-discovered" by oil geologists at the start of the twentieth century.

Preserved fossils---Drying (desiccation) Drying (desiccation)- Mummified bodies of animals including humans have been discovered in arid parts of the world. The soft tissues including skin and organs are preserved for thousands of years if they are completely dried.

Carbonized fossils Carbonized fossil – forms when organisms or parts, like leaves, stems, flowers, fish, are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock.

Trace fossils https://www.youtube. com/watch?v=v7vHAU rYzUU Trace fossils include footprints, trails, burrows, feeding marks, and resting marks. Trace fossils provide information about the organism that is not revealed by body fossils. Trace fossils are formed when an organism makes a mark in mud or sand. The sediment dries and hardens.

Archaeopteryx knew how to go out in style Archaeopteryx knew how to go out in style. Particulars of where the early bird died preserved the fossil in high definition.

What is the geologic time scale and why is important to us? https://www.youtube.com/watch?v=SY3MZ_wNFW8 The geologic time scale is a record of the major events and diversity of life forms present in Earth’s history. The geologic time scale began when Earth was formed and goes on until the present.

geologic time https://www.youtube.c om/watch?v=tkxWmh- tFGs At the end of each era a mass extinction occurred, many kinds of organisms died out, although there were other extinctions going on during each period of geologic time.

How do we know what organisms are in each geologic period? Using the fossil record, paleontologists have created an idea of the different types of common organisms in each geologic period.

How have Scientists been able to learn about life’s history? Nearly 4.6 billion years have passed since Earth’s formation. In that time, life has exploded from a few simple-celled organisms to a great variety of single-celled and multi-celled forms. Scientists know about life’s history from studying the fossil record and rock layers worldwide. This record can be arranged in a geologic time scale.

What is the Law of superposition? One of the most fundamental principles of archaeology is the Law of Superposition. The law states that rock layers that are younger will be deposited on top of layers that are older, given normal conditions of deposition. This law is the guiding principle of stratigraphy, or the study of geological or soil layers.

There are thousands upon thousands of layers in the earth's crust There are thousands upon thousands of layers in the earth's crust. However, scientists have grouped the layers into major groups. The most recent three layers are the Paleozoic, Mesozoic, and Cenozoic. These layers represent the last 500 million years of life on earth. These three layers make up a sort of 3-layer cake. Just like a cake, the bottom layer went down first, followed by the middle and the top. Since fossils progress from fish at the bottom to humans at the top, we have clear evidence that life evolved through time.