ELS- 2nd Quarter Flashcards
Different Features of the Ocean Floor:
5 items
Continental margin
Abyssal plains and abyssal hills
Mid-ocean ridges
Deep-ocean trenches
Seamounts and volcanic islands
submerged outer edge of the continent where continental crust transitions into oceanic crust
Continental margin
it is an extremely flat, sediment-covered stretches of the ocean floor, interrupted by occasional volcanoes, mostly extinct, called seamounts
Abyssal plains and abyssal hills
a submarine mountain chain that winds for more than 65,000 km around the globe
Mid-ocean ridges
narrow, elongated depressions on the seafloor many of which are adjacent to arcs of island with active volcanoes; deepest features of the seafloor.
Deep-ocean Trenches
One of the causes of Seafloor Spreading is the
Continental drift theory
(4) Evidence that supports continental drift theory:
Fit of the continent
Matching of rock units across ocean basins
Distribution of fossils
Paleoclimate evidence (evidence of tropical climates and past glaciations)
In ____, he advance the theory of seafloor spreading. He proposed that seafloor spreading separates at mid-ocean ridges where new crust forms by upwelling magma. Newly formed oceanic crust moves laterally away from the ridge with the motion like that of a conveyor belt. Old oceanic crusts are dragged down at the trenches and re-incorporated back into the mantle. The process is driven by mantle convection currents rising at the ridges and descending at the trenches.
This idea is basically the same as that proposed by ______ ______ in ____
1960
Harry Hess
Arthur Holmes in 1920
Evidences That Lead to the Proposal of Seafloor Spreading
5 items
High heat flow along mid-ocean ridge axes
Distribution of seafloor topographic features
Sediment Thickness
Composition of oceanic crust
Distribution of submarine earthquakes
it led scientists to speculate that magma is rising into the crust just below the mid-ocean ridge axis
High heat flow along mid-ocean ridge axes
distribution of mid-ocean ridges and depth of the seafloor
Distribution of seafloor topographic features
fine layer of sediment covering much of the seafloor becomes progressively thicker away from mid-ocean ridge axis; seafloor sediment are not as thick as previously thought
Sediment thickness
consists primarily of basalt
Composition of oceanic crust
earthquakes do not occur randomly but define distinct belts (earthquake belts follow trenches, mid-ocean ridges, transform faults)
Distribution of submarine earthquakes
It is a scientific theory that explains how landforms are created from the movement of the Earth.
Plate Tectonics
The Earth’s crust is divided into _____ large plates and into several smaller plates.
Seven
Driven by ______ __________, the lithospheric plates ride over the soft, ductile asthenosphere.
Mantle Convection
Submerged volcanoes are called ____ while those that rise above the ocean surface are called ____ ____ . These features may be isolated or found in clusters or chains.
Seamounts
Volcanic Islands
Primarily, earthquakes & volcanoes occur in a pattern that runs between continents & oceans.
The Coast
Major ____ ____ are often formed inside continents or near their edge.
mountain ranges
(3) Different types of Tectonic Plate Boundaries:
- Convergent Plate Boundaries
- Divergent Plate Boundaries
- Transform Plate Boundaries
Occur when plates collide with each other. Volcanoes & earthquakes commonly occur along these boundaries.
Convergent Plate Boundaries
Occur when plates move away from another. When they move apart, water or magma fills the space & creates new land.
Divergent Plate Boundaries
Are also known as sliding boundaries. They occur when plates slide creating a break in the earth’s surface. This can create a cliff & often causes earthquakes along faults.
Transform Plate Boundaries
Why do we we need to take a look back on the past?
“I believe that the more you know about the past, the better you are prepared for the future.” -Theodore Roosevelt
(3) Principles that Govern the Earth
- Catastrophism
- Gradualism
- Uniformitarianism
Volcanoes, floods, & earthquakes are examples of catastrophic events that were once believed responsible for mass extinctions & the formation of all landforms.
Catastrophism
Canyons carved by rivers show gradual change.
Gradualism
Is the idea that changes on Earth occurred by small steps (baby steps) over long periods of time.
Gradualism
Rock strata demonstrate that geologic processes long periods of time to cause great change.
Uniformitarianism
(2) Principles of Uniform:
- The major assumption of Geology
- Events of the past occurred the same way that they are occurring today.
Used to determine whether an object or event is older or younger than other objects or events.
Relative Dating
Relative Dating - Tool:
Sedimentary Rocks
Sedimentary rocks left undisturbed will remain in horizontal layers.
Law of Original Horizontality
When rocks are stacked in layers, the oldest rocks will be on the bottom & the newest rocks will be on top.
Law of Superposition
Geologic features, such as faults, & igneous intrusions are younger than the rocks they cut through.
Principle of Cross-cutting Relations
Used to measure the absolute use of an object or event by analyzing isotopes of radioactive elements.
Absolute Dating
Absolute Dating - Tool:
Radioactive
Unstable isotopes that break down stable isotopes &/or elements.
Radioactive Decay
Time needed for half of a sample of a radioactive substance to undergo radioactive decay.
Half-life
Indicates the life form present in different periods.
Geological Time Scale
System used by scientists to relate stratigraphy & time to any geologic event.
Geological Time Scale
Is roughly 4.1 billion years ago were 88% of the Earth’s history happened.
Precambrian
The perceived harshness of the primordial Earth happened during ____.
Hadean
Bombardment of meteorites and severe volcanic activities.
Hadean
Chaotic eon
Hadean
During this era, ocean and atmosphere were formed. The crust and core was also stabilized.
Hadean
____ was when the Earth became warm but the atmopshere contain only methane with litlte to no oxygen (orange atmosphere).
Archean
Most of Earth was still covered with water. Oceans were green due to abundance of iron and stromatolites.
Archean
Was when the atmosphere began to have oxygen, eukaryotes diversified, multicellular animals spread and continents began to drift away.
Proterozoic era
was when fossils of marine invertebrates (trilobites and brachiopods) were formed in sedimentary layers.
Paleozoic era