APES Test 4 Midterm Review Flashcards
Tectonic Plates
Scientists theorize that during the Paleozoic and Mesozoic Eras, the continents were joined together, forming a supercontinent known as Pangaea
Roughly 200 million years ago, Pangaea began to break apart
Today, it is believed that the Earth’s crust is composed of several large pieces of lithosphere– called tectonic plates – that move slowly over the mantle of the Earth
There are a total of a dozen or so tectonic plates that move independently of one another
The majority of the land on Earth sits above six giant plates; the remainder of the plates lie under the ocean as well as the continents
Some plates consist only of ocean floor, such as the Nazca plat, which lies off the west coast of South America, while others contain both continental and oceanic material
One ex. Of the latter is the North American plate where the US is located; this plate extends out to the Mid-Atlantic ridge
There is even a plate that is located exclusively within the Asian continent; its boundaries nearly coincide with those of Turkey
The largest plate is the pacific plate – it primarily consists of ocean floor, but also includes Mexico’s Baja Peninsula and southwestern California
The edges of the plates are called plate boundaries, and the places where two plates abut each other are where events like sea floor spreading and most volcanoes and earthquakes occur
There are three types of plate boundary interactions
Part I: Plate Tectonics
Earth is divided into crustal plates that move relative to one another
Convection currents are responsible for moving the plates
Circulation of heat within earth’s interior based on density differences
Relative motion (towards, away, or along) determines features at the respective boundary
Convergent Boundaries
Two plates move toward one another’
This results in subduction zones or mountain building events
Subduction zones result in volcanoes, usually several miles away from the boundary on the overriding plate
Mountain ranges are often tall and fast growing
Convergent zones are associated with earthquakes
One of the plates slides beneath the other, pushed deep into the mantle
Divergent Boundaries
Two plates move away from one another
This usually causes volcanoes at mid ocean ridges, where new lithosphere is created.
Earthquakes are possible with magma forcing its way to the surface, but are usually not severe
Rift valleys can form if this occurs on land
Transform Boundaries
Two plates slide along one another
These plates can become stuck and build up energy, typically in fault zones
Elastic rebound described how energy is released when faults slip, much like a rubber band
Many of earth’s worst earthquakes occur along transform faults, although subduction zone earthquakes can be equally or even more devastating
Plate collisions
What happens when plates collide depends on whether the collision happens between two oceanic boundaries, between two continental boundaries, or at an oceanic-continental boundary
Converging ocean-ocean and converging ocean-continent boundaries often result in subduction, in which a heavy ocean plate is pushed below the other plate and melts as it encounters the hot mantle
Converging continent-continent boundaries result in orogeny, the uplifting of plates that form large mountain chains as they crunch into each other
Ex. including the Himalayas (which were created by a collision between the plate carrying India and the Asian plate), the Urals of western Russia, the Alps of southern Europe, and the Appalachian Mountains of the Eastern U.S.
One important result of plate movement is the creation of volcanoes and earthquakes
Volcanoes
Volcanoes are mountains formed by pressure from magma rising from the Earth’s interior
Active volcanoes are those that are currently erupting or have erupted within recorded history, while dormant volcanoes have not been known to erupt during this period
It’s thought that extinct volcanoes will never erupt again
Events that produce volcanoes include subduction zones, rift valleys, and hot spots
Subduction zones creating volcanoes
Occur at convergent boundaries between oceanic and continental plates, or sometime between two oceanic plates
The subducting plate is recycle into new magma, which rises through the overlying plate to create volcanoes inland
Rift valleys making volcanoes
Occur at divergent boundaries, usually between two oceanic plates
New ocean floor is formed as magma fills in the gap between separating plates
Thick magma rising from rit valleys is made of basaltic minerals and forms pillow lava upon contact with the cold ocean water
Rift valleys may also occur between continental plates; a prominent example is the Great Rift Valley of eastern Africa, which gave rise to the Mount Kilimanjaro and other volcanoes
Hot spots making volcanoes
Do not form at plate boundaries
Instead, they are found in the middle of tectonic plates, in locations were columns of unusually hot magma melt through the mantle and weaken the Earth’s crust
The Hawaiian islands continue to form over a hot spot beneath the Pacific plate
Volcanoes over oceanic hot spots are basaltic, resulting in milder eruptions; while volcanoes over continental hot spots are characterized by rhyolitic rocks, which produce more violent eruptions
Tsunamis
Large volume of water displacement from some energy input, can be earthquakes
Other tsunami causes could include volcanic eruptions, NEO impacts, and even human caused
Tsunamis can only be predicted on short notice and are a serious threat to life and property
Soil
oil is a thin layer of matter that holds nutrients, filters water, and provides a structural foundation for plants to grow in
Plays a crucial role in the lives of the plants, animals, and other organisms and acts as an essential link between the abiotic components of the world and its biotic components
Plays an active role in the cycling of nutrients
Also performs task of protecting water quality – soil effectively filters and cleans water that moves through it
Soil is more than just dirt
Soil is actually a complex, ancient material teeming with living organisms
Many soils are tens of thousands of years old
A typical soil is about 45% mineral in the form of rocks broken down into tiny particles, about 25% air and 25% water which fill the pores between soil particles, and about 5% organic matter both living and dead (bacteria, protozoa, algae, fungi, and large organisms like earthworms)
Can be categorized according to a number of physical and chemical features, including color and texture
There are many ways to test soil taht can help people make decisions about its use
Where does soil come from?
Physical weathering
Any process that breaks rock down into smaller pieces without changing the chemistry of the rock
The forces responsbile for physicl weathering are typically wind and water
Chemical weathering
Occurs as a result of chemical reactions of rock with water, air, or dissolved minerals
Chemical processes result in minerals that are broken down or restructured into different minerals
This type of weathering tends to dominate in warm or moist environments
One ex. Of chemical weathering is rust, which forms when iron and other metallic elements come in contact with water
Biological weathering
Weathering that take solace as the result of activities of living organisms, which may act through physical or chemical means
When tree roots enlarge cracks in rocks as they grow, that is physical
When plant roots or lichens growing on rocks release organic acids that dissolve minerals, that is chemical
Soil Residual vs. Transported
Residual will form on bare rock- this may occur, for example, during primary ecological succession
Transported soil may occur when glacial till is transported to an area- a mix of sand, silt, clay in various compositions- could also form from sediment transported by streams or wind
