Umm Flashcards
What was earth’s first atmosphere like?
Almost all hydrogen and helium and they were very hot so they escaped earth’s atmosphere.
What was Earth’s second atmosphere?
ots of volcanic activity, so there was CO2, water vapor (formed clouds), and ammonia. Carbon dioxide dissolved into the oceans and simple bacteria thrived off of the sun and carbon making oxygen.
3rd atmosphere?
Our current atmosphere, made up of 78% of nitrogen, 21% oxygen, and 1% trace gasses. Plants and animals can thrive in these conditions.
*What is cyanobacteria?
Algae that was the first thing that photosynthesize.
What is paleontology?
the study of the history of life on Earth as based on fossils
When was the first evidence of life?
4.3 billion years ago
When did the first animal appear?
2.5 billion years ago
What was the Cambrian radiation “explosion”?
First modern day animals
What fossils are found in Virginia?
Paleozoic- marine, mesozoic- dinosaur, Cenozoic- mammals, carnivores.
Place the organisms in geologic time order of appearance: Algae, Bacteria, Bird, Fish, Reptile, Human
- Bacteria 2. Algae 3. Fish 4. Repitle 5. Bird 6. Human
What is radioactive dating?
Absolute age of fossils shown through radioactive decay.
What is a daughter isotope?
What the decaying particles are turning into
What is a half-life?
The time it takes for half of the particles to decay.
Carbon dating:
dating organic matter found within the rock
Carbon dating:
dating organic matter found within the rock
What is absolute age?
Numerical number for the age of fossil
What are beds?
Sedimentary rock layers.
Bedding planes-
Boundaries between beds
Relative age-
Age of an object relative to the age of objects around it- not numerical
Law of superposition-
Youngest rock is at the top, oldest is at the bottom
Law of original horizontality
Rock layers left undisturbed will stay horizontal
Unconformity-
Missing piece in geological history- weathering, erosion, ect.
Law of crosscutting-
A fault or igneous intrusion is always younger than the rock layers it cuts through
Radiometric Dating:
comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope
Isotopes
same element but different numbers of neutrons
Trace fossils:
a fossilized mark that formed in sedimentary rock by the movement of an animal on or within soft sediment(burrows)
Index fossil-
Fossil that shows the exact age of a layer. Short lived, widespread, adaptable, easily recognizable.
Types of trace fossils?
Footprints, burrows, and tracks
Molds
empty cavities of organisms
Casts
the empty cavities are filled with sand or mud
