The earth and beyond
Introduction to the free
National Curriculum Science Syllabus
"The Earth And Beyond"
What is it?
Why Study the Earth?
Earth Materials and Processes
Principle of Uniformitarianism
Energy Heat Transfer
The Earth -- What is it?
Internal Structure of the Earth
Surface Features of the Earth
adapted to HTML from lecture
notes of Prof. Stephen A. Nelson Tulane University
Things can change drastically!
Processes range from those that occur rapidly to those that occur slowly
- Examples of slow processes
- Examples of faster processes
- Beach erosion during a storm.
- Construction of a volcanic cone
- Landslides (avalanches)
- Dust Storms
- Hydrologic Cycle
- Rain comes from clouds - falls on surface, picks up sand, silt and clay, carries particles to river and into ocean. Water then evaporates to become clouds, which move over continents to rain again.
- Rock Cycle
- Rates -- rates of processes may change over time for example a river might deposit 1 mm of sediment /yr at if we look at it today. but, a storm could produce higher runoff and carry more sediment tomorrow. Another example: the internal heat of the Earth may have been greater in the past than in the present -- rates of processes that depend on the amount of heat available may have changed through time.
- Observations -- we may not have observed in human history all possible processes. Mt. St. Helens Example. Size of Earthquakes example.
surface rocks started out as
rocks- rocks produced by crystallization from a liquid. When igneous
rocks are exposed at the surface
they are subject to weathering
(chemical and mechanical processes that reduce rocks to particles).
moves particles into rivers and oceans where they are deposited to
rocks. Sedimentary rocks can be
buried or pushed to deeper levels
the Earth, where changes in pressure and temperature cause them to
rocks. At high temperatures metamorphic
rocks may melt to become magmas.
Magmas rise to the surface,
crystallize to become igneous rocks and the processes starts over.
rocks are broken down
(weathered) into small
which are then carried by wind, water, ice and gravity. External
erosion operates at the Earth's surface. The energy source for this
is solar and gravitational.
that produce magmas,
earthquakes and build mountain ranges. Energy comes from the interior
the Earth, Most from radioactive
decay - nuclear energy.
Perhaps a better way of stating the Principle of Uniformitarianism is that the laws of nature have not changed through time. Thus, if we understand the physical and chemical laws of nature, these should govern all processes that have taken place in the past, are taking place in the present, and will take place in the future.
All processes that occur on or within the Earth require energy. Energy can exist in many different forms:
- Gravitational energy -- Energy released when an object falls from higher elevations to lower elevations.
- Heat energy -- Energy exhibited by moving atoms, the more heat energy an object has, the higher its temperature.
- Chemical Energy -- Energy released by breaking or forming chemical bonds.
- Radiant Energy -- Energy carried by electromagnetic waves (light). Most of the Sun's energy reaches the Earth in this form.
- Atomic Energy -- Energy stored or released in binding of atoms together. Most of the energy generated within the Earth comes from this source.
- Conduction - atoms vibrate against each other and these vibrations move from high temperature areas (rapid vibrations) to low temperature areas (slower vibrations).- Heat from Earth's interior moves through the solid crust by this mode of heat transfer.
- Convection - Heat moves with the material, thus the material must be able to move. The mantle of the Earth appears to transfer heat by this method, and heat is transferred in the atmosphere by this mode.
- Radiation - Heat moves with electromagnetic radiation (light) Heat from the Sun or from a fire is transferred by this mode
and pressure increase with
depth in the Earth. Near the surface of the Earth the rate of
in temperature (called the Geothermal Gradient) ranges from
15 to 35oC per kilometer. Temperature at the center
of the Earth is about 4500oC
- Crust - variable thickness and composition
- Continental 10 - 50 km thick
- Oceanic 8 - 10 km thick
- Mantle - 3488 km thick, made up of a rock called peridotite
- Core - 2883 km radius, made up of Iron (Fe) and small amount of Nickel (Ni)
Lithosphere - about 100 km thick (deeper beneath continents)
Asthenosphere - about 250 km thick to depth of 350 km - solid rock, but soft and flows easily.
Mesosphere - about 2500 km thick, solid rock, but still capable of flowing.
Outer Core - 2250 km thick, Fe and Ni, liquid
core - 1230 km radius,
Fe and Ni, solid
All of the above is known from the way seismic (earthquake waves) pass through the Earth as we will discuss later in the course.
Land covers remaining surface with average of 0.8 km above sea level
- Continental Shelf, Slope, and rise
- Abyssal Plains
- Oceanic ridges
- Oceanic Trenches
- Tectonics = movement and deformation of the crust, incorporates older theory of continental drift.
- Plates: are lithospheric plates - about 100 km thick, which move around on top of the asthenosphere.
Boundaries occur at Oceanic Ridges, where new Oceanic
lithosphere is formed and moves away from the ridge in opposite
Convergent Boundaries occur where oceanic lithosphere is pushed back into the mantle, marked by oceanic trenches and subduction zones.
Two types are possible -
Collisions: may occur at a convergent boundary when plates of
lithosphere collide to join two plates together, such as has occurred
where the Indian Plate has collided with the Eurasian Plate to form the
Plate tectonics explains why earthquakes occur where they do, why volcanoes occur where they do, how mountain ranges form, as well as many other aspects of the Earth. It is such an important theory in understanding how the Earth works.