The document discusses Earth's structure and composition. It describes the four main systems - the geosphere, hydrosphere, atmosphere, and biosphere. It then focuses on describing the geosphere and hydrosphere in more detail. The geosphere is described as the solid portion of Earth, including its internal structure and surface features. The hydrosphere is the total amount of water on Earth, including the water cycle by which water circulates between the oceans, atmosphere, and land. Water is found in different states and the cycle involves evaporation, condensation, precipitation, and the collection of water.

1. EARTH'S
STRUCTURE AND
COMPOSITION

2. The Systems of Earth
i
geosphere,hydrosphere,
atmosphere, and biosphere
Gaia hypothesis

3. The Geosphere
• The geosphere is the solid portion of Earth that includes the interior
structure, rocks and minerals, landforms, down to the deep depths
of the core and the processes that shape Earth's surface.
• All the continents and the ocean floor are also considered part of the
geosphere. Essentially, this is the solid ground on Earth. Scientists
that study this part of Earth are called geologists.
• It should be clear that the term geosphere covers all of the solid
parts of Earth both on its surface up to the deeper depths of the
core, as opposed to the "lithosphere" which covers only Earth's
crustal part and upper mantle.

4. Geosphere's Internal Structure and Surface Features
• Earth has three main layers: the crust, mantle, and core.
The different layers change in density, mineral
composition, and thickness with depth.
• Modern technology has allowed the dentification of
materials in the interior of Earth through seismic waves.
• there are two types of waves traveling through Earth: the
p-waves, which travel fast through both solids and
liquids
• and the s-waves, which slowly travel only through solids.
• Seismologists and volcanologists
study the components of Earth through seismic waves.

5. Crust
• The crust consists of a 5- to 70-km thick layer of oceanic and continental crust
overlaying another thick layer of rocks and metals.
• The continental crust is thicker than the oceanic
crust.
• Most of the crust is composed of elements that include oxygen, silicon,
aluminum, iron, calcium, sodium, potassium, and magnesium.
• These are the same elements we know now as
inorganic materials that we process to produce
things we commonly use today, such as glass
(SiO₂), concrete (CaCO), and steel.

7. Mantle.
• The mantle is made of solid rock. It is also considered the largest part of
Earth, and makes up 84% of Earth's total volume.
• It lies between the extremely hot core and the thin outer layer of the
crust.
• At the upper part of the mantle directly below the crust is the
asthenosphere.
• The extreme temperature and pressure in the asthenosphere causes the
rocks to become ductile and thus move like liquid.
• The asthenosphere radiates heat from the mantle toward the surface. The
flow of molten rocks forces some brittle parts of the crust to break,
causing faults to form.
• Some rigid parts of the crust, on the other hand, just "float" or move
about slowly on this liquid like layer supporting the movement of plates as
described in the plate tectonics theory.

8. A xenolith is a piece of
rock trapped in another
type of rock.

9. • The rocks that make up the mantle are made mostly of.
silicate minerals
• Common silicates found in the mantle include
pyroxene, olivine, and garnet.
• The limited knowledge that scientists have on the
mantle is derived from the xenoliths, or rocks
embedded within another rock.
• When magma flows from Earth's surface, it cools and
various rocks are formed.
• Rocks may be embedded in the magma as it cools.
• Apparently, the rocks trapped inside the magma
contains most of the primary rocks that originated from
the interior of Earth. Hence, these are thought to be
the rocks in the mantle.

10. • The transitional boundary between the
mantle and the core is known as the
Gutenburg discontinuity. It was named
after its German discoverer, Beno
Gutenburg (1889-1960).
• This boundary is not fixed because of
changes in heat flow.
• When heat in the mantle slowly
dissipates, the molten core gradually
solidifies and shrinks, moving this
boundary deeper and deeper within
Earth's core.

12. • The core is made up of iron (Fe)and nickel (Ni).
• The iron in the outer core is in liquid form, which is why the iron core is
known to be liquid while the inner core is solid.
• The iron is particularly important because it is the primary source of Earth's
magnetic field.
• The magnetic field, particularly in the outer core, extends outward to
protect Earth from the solar winds by deflecting these winds towards outer
space.
• Without this magnetic field, solar winds could destroy Earth's atmosphere
and will destroy all living forms on the planet. Similar to the discontinuities
discovered in the other layers, there is also a transitional boundary
between the inner and the outer core-the Lehmann discontinuity which
was discovered in 1936 by Danish seismologist Inge Lehmann.
• When large earthquake occurred near New Zealand, Lehmann studied the
shock waves and realized that these waves had traveled some distance into
the core and then bounced off some kind of boundary. With layer that
there indeed lies a unique this distinct behavior of the waves, Lehmann
believed separates the liquid outer core from the solid inner core.

14. HYDROSPHERE
• The hydrosphere is the total amount of water found on Earth. This includes water in various forms-
whether in ice, vapor, or liquid - found on or below the surface of Earth and in gas in the
atmosphere. Water covers 70% of the entire Earth's surface and most of it is ocean water.
• Water has been associated with the existence of life. When water or traces of water are found in
other planets, the possibility of life is always speculated. It is a critical component for most
organisms given that drying up would mean dying.
The Hydrological Cycle
• Water circulates everywhere on Earth (see figure 2.6). This is made possible by the interaction of
energy and matter that prompts the transformation of water from one phase to another, allowing
it to circulate and travel to different regions on the planet.
• Water moves through the hydrosphere in a cycle. The sun's energy is the power that drives the
water cycle. Light and heat cause water to evaporate from oceans, lakes, rivers, and other sources
of surface water.
• Water on the surface of Earth changes from its liquid state to its gaseous state or water vapor
whentemperature increases. The water vapor rises to the atmosphere as gas (evaporation). When
water vaporcombines with tiny particles of dust, smoke, or salt in the air, water droplets form.
When the waterdroplets increase in number, they form clouds. As the water droplets form clouds,
precipitation mayoccur. Depending on condensing temperature changes, water may fall from the
atmosphere in the form ofrain or snow. Liquid water goes back to rivers, lakes, and oceans or seeps
through rocks and soils to reachthe water table. Water underground finds its way back into the
ocean through slopes and cracks.

15. In some regions where temperature is
below zero degrees Celsius, solid water
is found in glaciers. Precipitation in the
form of snow may recrystallize to form
thick masses of ice called glaciers which
contain most of Earth's water supply.
Again, when water is in the atmosphere,
it can during condensation and
evaporation and start the cycle all over
again. The whole process is called the
hydrological or water cycle. Because
organism depend mainly on water for
survival, the hydrological cycle makes
possible the accessibility of water for
organisms in different areas of Earth.

16. Distribution of Water on Earth
All the water found on Earth are natural but not all is considered safe for
drinking. In fact, only 2.5% of the world's water is considered freshwater.
Water is divided into two groups: surface water and groundwater. Surface
water, as the name implies, is found on Earth's surface, as opposed to
ground water which is found below the ground. The surface water and
groundwater also differ in the type and amount of minerals contained in
them.

17. • Surface water may either be salt water or freshwater.
• Salt water has higher salt content and is found in larger bodies
of water such as oceans, seas, bays, and gulfs.
• Freshwater, on the other hand, is found in lakes, rivers, streams,
springs, and falls. Because of its lower salt content, freshwater
best source of drinking water for all organisms. Sadly,
freshwater accounts for only 2.5 % of the world’s water. This is
precisely the reason for advocacies on water conservation.
While it is evident that water is found almost everywhere on
Earth, most of it is salty, and thus is not readily fit for drinking.