Geology and Earth Science Flashcards
Magma Intrusions
Volcanic Activity
Fault Lines
Earthquake/Tectonic activity
Absolute Time
The actual or estimated date of an event.
[Ex. The Wooly Mammoth first appeared 1.7 million years ago (MYA) ]
Relative Time
Placing historic evens in proper sequence order, relative of other events.
The Geologic Time Scale is organized into periods of relative time.
Fossils
Preserved remains or traces of living things
Index Fossils
A special fossil that allows geologists to determine the relative age of rock layers in which they are found.
(They can match up rock layers at locations that may be far apart).
Fossil Dating
Carbon-14 is used to determine the age of past-living things. It’s can date as far back as 60,000 years.
Carbon-14
Used for fossil dating, the amount of carbon-14 remaining determines how long ago an organism lived. Carbon-14 decays over time.
(The less carbon-14 there is, the longer time ago).
3 Types of Rocks:
- Igneous
- Sedimentary
- Metamorphic
Igneous Rock
Form from the cooling of liquid rock; made from lava. These are classified based on composition and texture.
There are intrusive and extrusive igneous rocks.
Intrusive Rock
A type of igneous rock which cools inside the Earth and often have large crystals inside them.
Extrusive Rock
A type of igneous rock which cools outside the Earth, usually from volcanoes.
Half Life
The time it takes for half of a radioactive element’s atoms to decay (Carbon-14).
Laws of Relative Dating
Used to identify the relative age of rock layers.
- Law of Superposition
- Law of Cross-Cutting
- Law of Faulting
Law of Superposition
In undisturbed sedimentary rock, the youngest rock layers are on top and the oldest rock layers are on the bottom.
Law of Cross-Cutting
Intrusive Igneous rock is younger than the rock it cuts through.
- Cools slower, inside the Earth.
Extrusive Igneous rock is younger than the rock it lies on.
- Cools faster, outside the Earth.
Law of Faulting
A fault is a crack in the Earth’s crust along which movement has occurred.
Faults are younger than the rock they have broken.
Unaffected rocks will be older than the rocks made due to faults.
Unconformity
A gap in the rock record (Some rock layers are missing) usually caused by weathering and erosion.
Theory of Plate Tectonics
Earth’s rigid crust and upper mantle is broken into large plates, which move slowly at a constant pace over long periods of time.
Types of Plate Boundaries:
- Convergent - Places where two plates are moving towards each other
- Divergent - Places where two tectonic plates separate
- Transform - Places where two plates slide horizontally past each other.
Theory of Continental Drift
All continents had once been joined as a single landmass that split apart millions of years ago.
Evidence includes rock formation matches, climatic changes, and glacial erosion.
Theory of Seafloor Spreading
The new ocean crust is formed at ocean ridges and destroyed at trenches.
Evidence shows that rocks at the midocean ridge are younger than that by the trenches, and this is driven by convection currents.
Divergent Boundaries:
Plate boundaries which separate (“diverge”) from each other.
On a continent, this forms a rift valley.
Under the ocean, a midocean ridge is formed.
Convergent Boundaries:
Plate boundaries which push against each other. The three types are…
- Ocean/Continental
- Ocean/Ocean
- Continental/Continental
Ocean/Ocean Convergent Boundaries:
- Subduction creates a deep-sea trench
- Melted crust above the trench rises to form an arc of volcanic islands.
Ocean/Continental Convergent Boundaries:
- Oceanic plate subducts under the continental plate since it is denser.
- A volcanic mountain range forms on the land above the subduction zone.
Continental/Continental Convergent Boundaries:
- A folded mountain range is formed when two continental plates collide
- An example is the Himalaya Mountains.
Transform Boundaries:
- Crust is only deformed or fractured; characterized by Earthquakes
- An example is the San Andreas Fault (California).
Asthenosphere
The partially molten layer of the mantle. Lithosphere lies on top, and is the brittle crust and uppermost mantle.
Convection Currents
Tectonic plates move…
- The rising part of the convection current spreads out as it reaches the upper mantle which lifts and splits the lithosphere at divergent plate boundaries.
- The downward part of the convection occurs where a sinking force pulls tectonic plates downward at convergent boundaries.
Ridge Push
The force created by the weight of the uplifted ridge which pushes an oceanic plate towards a trench (at a subduction zone).
https://images.app.goo.gl/z6Jg2Njs8BAAtWHu5
Weathering
The break-up of rock due to exposure to the atmosphere (Water and gases).
Mechanical is when a rock is broken down, chemical is when the minerals are changed into different substances.
Erosion
Removal and transport of Earth materials by natural agents (glaciers, water, winds, etc…).
Weathering and Soils:
+Regolith
+Bedrock
+Soil
+Regolith - Layer of weathered rock fragments that covers most of the Earth’s surface.
+Bedrock - Solid, unweathered rock that lies beneath the regolith
+Soil - Mixture of weathered rock particles and organic material. Made up of sand, clay, or silt.
Soils:
+Clay
+Silt
+Sand
+Soil Pyramid
+Clay - Smallest particle size; impermeable
+Silt - Medium particle size; found around river banks and river beds
+Sand - Largest particle size; weathered from rocks containing quartz
+Soil Pyramid - Determine percentages of sand, clay, and silt in a soil sample.
Soil Profile:
- A horizon
- B horizon
- C horizon
Cross section in which layers of soil and bedrock can be seen.
A horizon - Consists of topsoil rich in organic material
B horizon - Reddish/Brown topsoil rich in minerals and nutrients
C horizon - Deepest layer consisting of broken and solid, un-weatherable bedrock.
Slab Pull
The process in which the weight of the subducting plate helps pull the trailing lithosphere into the subduction zone.
https://images.app.goo.gl/z6Jg2Njs8BAAtWHu5
Volcano
- Magma
- Lava
A mountain or opening in Earth’s crust from which lava erupts.
– Magma - A mixture of molten rock, suspended mineral grains, and dissolved gases deep beneath Earth’s surface.
– Lava - Molten rock that has reached Earth’s surface
Anatomy of a Volcano:
- Vent
- Crater
- Caldera
- Magma Chamber
Vent - The opening in the crust through which lava erupts
Crater - Bowl-shaped depression around the vent
Caldera - Larger depressions around a vent where the volcano has collapsed into the magma chamber
Magma chamber - Area under the volcano which holds the magma.
Types of Volcanoes:
- Formation
- Description
- Ex.
Shield Volcano
- Basaltic lava accumulates
- Broad with gently sloping sides
- Kilauea in Hawaii
Cinder Cone
- Ejected tephra falls back to earth and piles up
- Small, but steep-sided
- Paricutin in Mexico; Izalco in Central America
Composite
- Tephra eruptions alternate with lava flows
- Large and steep
- Mt. St. Helens
Tephra
- Rock fragments thrown into the air during a volcanic eruption
- Tephra classified by size…
Dust –> ash –> lapilli –> bombs –> blocks
Pyroclastic Flow
- An eruption of gas, ash, and other tephra
- These types of eruptions can be extremely violent and deadly because the pyroclastic flow moves very fast and is very hot.
Volcanoes occur at…
Convergent boundaries
- Ocean plates subduct under other plates and melt to form magma
- Location – the Pacific Ring of Fire, the Mediterranean Belt
Divergent boundaries
- As plates move apart, magma is forced upward into fractures and faults
- Location – East Africa Rift Valley, Mid-ocean ridges, Iceland
Hot Spots
- Magma rises from usually hot regions of Earth’s mantle in the center of a plate
- Location – Hawaii. Yellowstone
Magma Type:
- The higher the silica content, the higher the viscosity (resistance to flowing)
- …the greater the explosiveness!
Pluton (and types)
An intrusive igneous rock body
- Batholiths
- Stocks
- Laccoliths
- Sill
- Dike
Batholiths
- A batholith is the largest of plutons common in the interiors of major mountain chains
- Ex. Yosemite – Part of the Sierra Nevada Batholith
Stocks and Laccoliths
- Stocks – Irregularly-shaped plutons similar to batholiths but smaller.
- Laccoliths – Mushroom-shaped plutons with a round top and a flat bottom
