EARTH SCIENCE at SPRING VALLEY HIGH SCHOOL
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UNIT V: EARTHS HISTORY
«1. Learn to sequence and correlate rocks using such rules as superposition, original horizontality, cross cutting relationships, included fragments, etc.
a. dating is an attempt to put geologic events or structures into proper chronological order.
b. The Principal of states that the geologic processes that occurred in the past are basically the same as those that are occurring now.
c. Original - sedimentary rocks generally form in horizontal layers, with new layers forming on top of existing layers.
d. The Principle of states that the bottom layer of a series of sedimentary layers is oldest, unless the series has been overturned or has had older rock thrust over it.
e. Rock layers are than igneous intrusions that cut through them or igneous extrusions that are above them.
f. Rocks are than faults, joints, folds, or veins that appear in them.
g. Fragments of unmelted material occurring within a rock are than the rock.
h. In sedimentary rocks, the sediments are than the cements (matrix) that bind them and the rock formation itself.
i. is the process of showing that rocks or geologic events occurring at different locations are of the same age.
j. In correlation, rock layers may be traced from one location to another directly by walking the , thus showing the continuity of layers.
k. Rocks may be on the basis of similarities in appearance, composition, and position in relation to other layers.
«2. Recognize unconformities, their formation and significance.
a. An is a buried erosional surface.
b. Where the surface has been away, there is a gap, in the rock layer.
«3. Describe the processes of fossil formation.
a. are the remains or impressions of ancient plants and animals.
b. Petrification- the process of turning plant material into stone by infiltration with water carrying mineral particles without changing the original shape; ex/ petrified
c. Carbonization- the weight of the sediments squeezes out the water and gas from plant matter and leaves an imprint of .
d. Impressions- molds; ex/ indentations left behind in mud
e. Casts- a replica of an organism created when minerals use the organism as a mold to create the replica. For example, a shell fills with minerals, the shell dissolves away and the cast (inside of the shell) is left behind.
f. Preservation in - a hard, translucent, yellow, orange, or brownish-yellow fossil resin. Formed from hardened sap, resin, or gum from conifers (ex/pine trees); amber is a valuable fossil record of ancient plants and animals - many species have been found trapped inside amber chunks dating over hundred of millions yrs old.
g. Tracks- ex/ footprints
h. Burrows- tunnels or holes that small animals in the ground; an excellent last name.
i. Fossils are found in rocks.
j. The special conditions that favor preservation are rapid and the possession of parts such as shells, bones, or teeth.
«4. Understand how to interpret paleoclimate and environment from fossil evidence.
a. in rocks provide information about the environment in which they formed.
b. Animals and plants that live in the are very different from those that live on land. The same is true for fossils of ancient life forms.
c. The presence of marine fossils at high elevations indicates that has occurred.
d. The presence of shallow water marine fossils at great depths indicates that has occurred.
e. The presence of fossil coral indicates that there was once a shallow tropical . Coral needs warm, shallow, clear, salty water to live (not too salty).
«5. Locate and interpret the fossil record and geologic history of New York State using the ESRT (pages 2,3,8 and 9).
a. should be able to determine the age the rocks at any location in NY.
b. should be able to determine where specific fossils may be found in NY.
c. should be able to determine when important geologic events occurred in NY.
«6. Understand that geologic time is determined by the fossil record.
a. Long before geologists had the means to recognize and express time in numbers of years before the present, they developed the geologic time .
b. Geologists have divided the Earth's history into time units based upon the record. These units of time often begin and end with major .
c. The geologic time scale is commonly presented in chart form, with the time and event at the bottom and the at the top.
d. Units of time, from largest to smallest: Eons, , Periods, Epochs.
e. The largest units of the geologic time scale are called . Together, the Archean (Greek ancient) and Proterozoic (Greek earlier life) are commonly referred to as the . The Phanerozoic (Greek visible life") began about 544 million years ago.
f. The Phanerozoic eon is divided into the following eras: Paleozoic ("ancient life"), ("middle life" Age of Reptiles), and Cenozoic ("recent life").
* Period and Tertiary Period- The several geologic eras were originally named Primary, Secondary, Tertiary, and Quaternary. The first two names are no longer used. Tertiary and Quaternary have been retained but used as period designations.
* Neogene- An Age of Grasses
* Paleogene- The Early Age of Mammals
* - New Dinosaurs - Flowering Plants - Derived from Latin word for chalk (creta) and first applied to extensive deposits that form white cliffs along the English Channel.
* Period- The Triumph of the Dinosaurs- Named for the Jura Mountains, located between France and Switzerland, where rocks of this age were first studied
* Period- Taken from the word trias in recognition of the three distinct layers within these rocks in Germany.
* Period- Named after the province of Perm, Russia, where these rocks were first studied.
* - means coal bearing. It is the age of great forests.
* Period- Named for the State of Pennsylvania where these rocks have produced much coal.
* Period- Named for the Mississippi River Valley where these rocks are well exposed.
* Period- "the age of fishes" Named after Devonshire, England, where these rocks were first studied.
* and Periods- Named after Celtic tribes, the Silures and the Ordovices that lived in Wales during the Roman Conquest.
* Period- Taken from the Roman name for Wales (Cambria) where rocks containing the earliest evidence of complex forms of life were first studied.
h. If you pretend that Earths history took place in a single day, each minute on this twenty-four hour clock would represent about 3 million years:
* Midnight (4.6 billion years ago) Earth forms from cosmic dust
* 3:20 A.M. (3.96 billion years ago) age of oldest ever found
* 9:23 P.M. (500 million years ago) first animals with backbones
* 11:00 P.M. (190 million years ago) age of the
* 11:35 P.M. (80 million years ago) Rocky Mountains start to form
* 11:58 P.M. (6 million years ago) small stream begins carving Grand
* 11:59 P.M. and 26 sec. (1.8 million years ago) earliest appear
* 11:59 P.M. and 45 sec. (750 thousand years ago) humans begin using fire
* 11:59 P.M. and 59 sec. (20 thousand years ago) last Age
i. You should be able to date rocks based upon the fossils within them using the ESRT.
«7. Understand that fossils reveal the process of evolution.
a. If we begin at the present and examine older and older layers of rock, we will come to a level where no of humans are present.
b. If we continue in time, we will successively come to levels where no fossils of flowering plants are present, no birds, no mammals, no reptiles, no four-footed vertebrates, no land plants, no fishes, no shells, and no animals.
c. - the process by which all forms of plant and animal life change slowly over time because of slight variations in the genes that one generation passes down to the next; living beings have changed through time and older species are ancestors of younger ones.
d. The pattern of of life-forms on Earth is at least partially preserved in the rock record.
e. Fossil evidence indicates that a wide variety of life-forms has existed in the past and that most of these forms have become .
f. Human existence has been very compared to the expanse of geologic time.
«8. Explain the significance of index fossils and volcanic ash in correlation.
a. fossils are the remains or imprints of organisms that existed for a relatively short period of time, but were widely distributed over the Earth. They identify and date the layers in which they are found.
b. Layers of volcanic in rock can be useful in correlation because they were deposited over a large area in a very short period of time.
c. An excess of the element iridium, discovered in a layer of rocks formed at the end of the Cretaceous period 65 million years ago, suggests that an struck the Earth at that time. The consequences of the impact may have played a role in the Cretaceous extinctions. This layer, called the K-T Boundary, can be used to rock layers.
«9. Understand that unconformities reveal an incomplete rock record.
a. If rock layers are eroded away, there is a in the rock record.
b. Information is where unconformities are found.
«10. Understand that subsidence/ submergence leads to deposition; uplift/emergence leads to erosion.
a. When land (lowers) or submerges (drops under ), deposited sediments usually begin to build up.
b. The presence of rocks indicates that subsidence or submergence has occurred in the past.
c. When rocks are out of the water (emergence), they are exposed to the agents of weathering and erosion.
d. The presence of erosion or an indicates that the crust uplifted/emerged in the past.
«11. Explain how radioactive decay causes heating in the Earths interior.
a. Most of Earths internal heat is created by the decay of elements that were trapped in the interior when the Earth first formed. These elements (for example Uranium, Thorium, Cesium and many others) spontaneously split apart into smaller elements and release energetic particles in a nuclear process called fission. The energetic particles released by fission collide with other atoms and produce heat.
b. The Earth can be thought of as a giant fission battery that is slowly running down as it uses up its original charge of radioactive elements. Eventually (in a couple of billion years), the Earths interior will and the planet will become geologically dead - as the Moon is today.
«12. Using the ESRT, understand half-life as a tool for measuring actual age. (see ESRT p.1)
a. Some rocks contain elements with atomic nuclei that undergo spontaneous (decrease of a radioactive substance).
b. An unstable radioactive isotope, called the , will decay and form stable daughter products.
c. The length of time for one-half of the nuclei of a radioactive isotope to decay is called the of the isotope.
d. If the half-life of the isotope is known, and the parent/daughter ratio can be measured, the of a sample can be calculated. A table of half-lives of commonly used radioisotopes is in the Reference Tables.
e. The age of a rock can be determined from the relative amounts of a radioisotope and its product.
f. Each radioactive isotope has unique properties and uses. , the radioactive isotope of carbon that is absorbed by living matter, is used to date very recent events. It can only be used to date thing that were once , recently.
g. Other elements occur in and metamorphic rocks.
h. Since rocks contain pieces of other rocks, they are difficult to date radioactively.
«13. Explain how the age of the Earth has been determined.
a. The oldest known rocks on Earth have been dated radiometrically at 3.96 years, and the oldest individual crystals at 4.3 billion years.
b. Scientists believe that the Earth is than this, but that more ancient rocks did not survive the molten conditions that prevailed after the planet's birth.
c. The oldest Moon rocks have been dated at about 4.5 years, and the oldest meteorites at 4.5 to 4.6 billion years.
d. On the basis of these results, along with calculations concerning radioisotopes in meteorites and in the Earth, scientists have concluded that the entire , including Earth and all the other planets, formed about 4.6 billion years ago.
«14. Know the evidence of past tectonic activity and interpret the sequence of plate motions using the ESRT. (ESRT p.9)