2021 Q2 Geologic Time Scale PDF

INDEX FOSSILS & GEOLOGIC TIMESCALE  Describe how index fossils (also known as guide fossils) are used to define and identify subdivisions of the geologic time scale (S11ES-Ii-j-38) OBJECTIVES 1. Describe how the Earth’s history can be interpreted from the geologic time scale. 2. Defi...

INDEX FOSSILS & GEOLOGIC TIMESCALE  Describe how index fossils (also known as guide fossils) are used to define and identify subdivisions of the geologic time scale (S11ES-Ii-j-38) OBJECTIVES 1. Describe how the Earth’s history can be interpreted from the geologic time scale. 2. Define fossils and its type. 3. Determine the guide fossils that are used to define and identify subdivision of the geologic time scale. 4. Track the Earth’s history using the geologic time scale. 5. Identify the different divisions in the geologic time scale..  means motive opportunity → Sequence of events  ROCK LAYERS and FOSSILS Geologic Time Scale (GTS) – a record of the life forms and geological events in Earth's history. Scientists developed the time scale by studying rock layers and fossils world wide. Radioactive dating helped determine the absolute divisions in the time scale.  Cyanobacteria – 3.5 B y/o What is the oldest fossil? ▪ FOSSIL is a preserved remains or traces of plants, animals, and other organisms from the past. ▪ PALEONTOLOGY – study of fossils ▪ FOSSIL RECORD – this are the history of life as documented by all fossils which preserved in sedimentary rock strata ▪ INDEX FOSSILS – serves as a guide or indicator of certain geologic periods. This are used to correlate the age of the rock strata. ▪ Fossilization – process by which the remains of ancient living things are turned to rock ▪ Paleontologist – a scientist who studies fossils and ancient life ▪ Sedimentary Rock – rock made of layers of tightly packed sand and clay ▪ Body Fossils – actual parts of plants and animals that have been turned to stone (i.e. bone, shells, leaves) ▪ Sandstone – a type of sedimentary rock that is made of sand ▪ Trace Fossil – a fossilized sign that a plant or animal once lived in an area (i.e. footprints) ▪ Porous – full of tiny holes that water, air, and light can pass through ▪ Mineralization – to convert into a mineral substance; to fill with a mineral substance  F O I S N S D I E L X S HOW DO FOSSILS FORM? 1.preservation of original remains 2.Permineralization 3.Molds and casts 4.Replacement 5.Compression.  HOW DO FOSSILS FORM? 1. Preserved Remains - Rarest form of fossilization  HOW DO FOSSILS FORM? 2. Permineralization - Most common method of fossilization  HOW DO FOSSILS FORM? 3. Molds and Casts - original bone or shell dissolves away, leaving behind a space in the shape of the shell or bone then the space may be filled with other sediments to form a matching cast in the shape of the original organism.  HOW DO FOSSILS FORM? 4. Replacement - original shell or bone dissolves away and is replaced by a different mineral  HOW DO FOSSILS FORM? 5. Compression - form when their remains are compressed by high pressure leaving behind a dark imprint on the fossil. 1. The fossilized organism must be easily recognizable. It must be easy to ID and look unique. 2. The fossils must be geographically widespread or found over large areas so that we can use them to match layers separated by huge distances. 3. The fossil must have lived for only a short time so that it appears in only a horizontal layer of sedimentary rocks.  Using Index Fossils to Correlate Rock Layer By correlating them, we now know that layers A, K, and Q are of the same age. So, to find the oldest rocks we look below them, and to find the youngest rocks we look above them. If we create a chart building our way up and down by looking directly above and below each layer, we will find the top and bottom. Instructions: Fill in the blanks, using vocabulary words. Jay, a famous p ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ t, was hiking in the Cordillera mountains searching for f ___ ___ ___ ___ ___ ___, which are remains of ancient life that have turned to stone. All of a sudden, the ground shook beneath him. Jay ran over a hill and saw that there had been a huge landslide. He went over to look at the piles of rocks and saw layers of s ___ ___ ___ s ___ ___ ___ ___, a type of sedimentary rock. Fossils are found in sandstone, so Jay was excited to search through the rocks! Just as he began to dig, he found fossilized bones. The bones had turned to stone through a process called ___ ___ s s ___ ___ ___ ___ ___ ___ ___ ___ ___. Jay saw that the fossils belonged to an Apatosaurus. These bones are examples of b ___ ___ ___ ___ ___ ___ ___ i l ___, which are fossilized parts of plants and animals. He also found a huge footprint, which is an example of a t ___ ___ ___ ___ f ___ ___ ___ ___ ___. Jay carefully removed the fossils from the rocks and donated them to a museum. THE GEOLOGIC TIME SCALE ▪ provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The detailed studies made of rocks throughout the world have allowed geologists to correlate rock units globally, and break them into time units. Cenozoic Era It is also known as the age of recent life or age of mammals. It has the most complete record of any era because the rocks are more accessible. Let’s Trace  major organism developed or became extinct in each section We live in the CENOZOIC ERA! ⚫Present day Earth is in the Cenozoic ERA and the Quaternary PERIOD in the Holocene EPOCH. ⚫Geologic time has NOT ended!!!!! EARTH’S HISTORY 1. Precambrian Time at 4.6 Billion Years Ago This period is MOST of Earth’s history. For nearly 4 billion years, during most of Precambrian time, no plants or animals existed. Multicellular organisms develop late in the Precambrian. 1. Precambrian Time at 4.6 Billion Years Ago a. Hadean – “hades”, considered as a chaotic eon mainly due to the meteorites that constantly hit Earth, causing most severe volcanic activities. 1. Precambrian Time at 4.6 Billion Years Ago b. Archean – Earth became warm, but the atmosphere contains only methane and only few to no oxygen; lasted for 1.3 Ga (Giga annum) 1. Precambrian Time at 4.6 Billion Years Ago c. Proterozoic – atmosphere began to have oxygen, eukaryotes spreads, multicellular animals appears, and the continents began to drift away, lasted for 1.9 Ga (Giga annum), 1 Ga (Giga annum) = 1 billion years 2. Paleozoic Era at 544 Million Years Ago PALEO = “ancient or early” LIFE EXPLODES! At the beginning of the Paleozoic era, all life lived in the oceans. Early invertebrates developed and later reptiles became dominant on land. Early plant included simple mosses, ferns, and cone-bearing plants. PANGAEA 3. Mesozoic Era at 245 to 65 Million Years Ago MESO = “middle” (Age of the Reptile/Dinosaurs) Dinosaurs lived along with the first mammals, birds, and flowering plants. Reptiles were dominant. 4. Cenozoic Era 65 mya to Present Day CENO = “recent” ZOIC = “life” The first humans appeared in the later part of the Cenozoic era, which continues today. The diversity of life forms increased. New mammals and birds appeared while other became extinct. Flowering plants became most common.  SUMMARY o Geologic time scale is a timeline that illustrates Earth’s past. o Geologic time scale describes the order of duration of major events on Earth for the last 4.6 billion years. o Geologic time scale was developed after the scientist observed changes in the fossils and rocks going from oldest to youngest sedimentary rocks. o Geologic time scale was divided into four divisions which include the Eons, Era, Period, and Epoch. o Eons is the largest division in the geologic time scale.