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Transcript of 09 Landforms
the study of Earth's physical structures and the processes that have created them.
The theory of plate
how forces within the planet create landforms. This theory views Earth's crust as divided into more than a dozen rigid, slow moving plates.
Three types of movements at plate boundaries are possible.
, the plates can move apart, or spread.
, the plates can collide.
the plates can move laterally. The movement of plates creates distinctive landforms.
Forces on Earth's Surface
Weathering and Erosion
Rocks break and decay over time in a process called
. Is usually slow and difficult to detect. Chemical processes cause some weathering.
Shapes on the Land
One way to better understand landforms is to divide them into three groups .
When Plates Collide
When two plates on the ocean floor collide, one slides underneath the other. This plate boundary is called a
, and the deep valley marking the plate collision is called a
, is divided into inner and outer layers. The inner core is solid. The outer core is mostly dense liquid metal, mainly iron and nickel.
Beyond the core is the
, the zone that has most of Earth's mass.
The uppermost layer is the
Although it is up to (40km) thick, the crust is comparatively thin.
Liquid rock within Earth is called
. When this liquid rock spills out onto the surface it is called
Magma erupts from vents called
The plates slowly move across the upper mantle. This process is called continental drift. The crust is subject to stresses that lead to melting, bending, and breaking.
A few spreading plate boundaries lie under continents. In these places, the crust stretches until it breaks, forming
Away from the oceanic ridges, rocks of the ocean floors gradually sink because they have no supporting heat below them, here we find
The continental surface extends under the shallow ocean water around the continents. These areas are called
. At the edges of the continental shelves, the seafloor drops steeply down to the abyssal plains.
Volcanoes often form longs rows and signal that a plate boundary is nearby .
Scientists use the theory of place tectonics to explain the long history of Earth's surface
Sometimes one of the plates is carrying a continent. In this case the heavier oceanic plate divides under the lighter continental plate. The squeezing of the continental plate causes volcanoes,
folds and faults
are places where rocks have been compressed into bends.
are places where rock masses have broken apart and moved away from each other.
The roots of trees can break rocks apart. Weathering breaks rock into smaller particles of gravel, sand, and mud called
Along with weathering, the other process changing landforms on Earth's surface is
, is the movement of surface material from one location to another. Water, wind, and ice cause rosion.
Thick masses of ice called
,also erode rock and move sediment.
Miss Paola Ruiz