Download Earth`s Systems: Ch

Earth’s Systems: Ch. 6, 18, 20
1) Easy: Investigate the properties of water and its effects on Earth’s materials and
surface processes. Apr. 15 Saul; Miguel
a) Determine the physical and chemical interactions between water (hydrologic cycle) and solid materials
(rock cycle). Physical interactions include erosion and deposition by rivers, erosion of soil due to soil
moisture content, or frost wedging by the expansion of water as it freezes. Chemical interactions include
chemical weathering and recrystallization (solubility of different materials) or melt generation (how water
lowers the melting temperature of most solids).
i) The abundance of liquid water on Earth’s surface and its unique combination of physical and chemical
properties are central to the planet’s dynamics. These properties include water’s exceptional capacity to
absorb, store, and release large amounts of energy, transmit sunlight, expand upon freezing, dissolve
and transport materials, and lower the viscosities and melting points of rocks.
How does water change Earth’s surface?
Ch. 6
- water can be found as a solid, liquid, and gas on Earth p. 106
- The ancient oceans had a vast amount of dissolved iron, which is much more soluble in water in its
unoxidized state. Oxygen released into the oceans combined with the dissolved iron, changing it from a
more soluble to a less soluble form. No longer dissolved in the water, the iron settled (precipitated) to the
bottom of the oceans and became part of deposits that slowly were turned into rock. Over millions of years,
these deposits formed the thick bands of iron ore that are mined today all around Earth. p. 108
- Throughout the 4.6 billion years of Earth’s history, rocks and soils have been continuously created,
maintained, changed, and destroyed by physical, chemical, and biological processes. This is another
illustration that the biosphere is a dynamic system, not in steady state. Collectively, the processes
responsible for formation and change of Earth materials are referred to as the geologic cycle (Figure 6.10).
The geologic cycle is best described as a group of cycles: tectonic, hydrologic, rock, and biogeochemical. p.
113
- The hydrologic cycle (Figure 6.13) is the transfer of water from the oceans to the atmosphere to the land
and back to the oceans. It includes evaporation of water from the oceans; precipitation on land; evaporation
from land; transpiration of water by plants; and runoff from streams, rivers, and subsurface groundwater.
Solar energy drives the hydrologic cycle by evaporating water from oceans, freshwater bodies, soils, and
vegetation. Although water on land and in the atmosphere accounts for only a small fraction of the water on
Earth, this water is important in moving chemicals, sculpting landscape, weathering rocks, transporting
sediments, and providing our water resources. p.115-116
- The rock cycle consists of numerous processes that produce rocks and soils. The rock cycle depends on the
tectonic cycle for energy, and on the hydrologic cycle for water. As shown in Figure 6.14, rock is classified
as igneous, sedimentary, or metamorphic. These three types of rock are involved in a worldwide recycling
process. Internal heat from the tectonic cycle produces igneous rocks from molten material (magma) near
the surface, such as lava from volcanoes. When magma crystalized deep in the earth the igneous rock
granite was formed. These new rocks weather when exposed at the surface. Water in cracks of rocks
expands when it freezes, breaking the rocks apart. This physical weathering makes smaller particles of rock
from bigger ones, producing sediment, such as gravel, sand, and silt. Chemical weathering occurs, too,
when the weak acids in water dissolve chemicals from rocks. The sediments and dissolved chemicals are
then transported by water, wind, or ice (glaciers). Weathered materials that accumulate in depositional
basins, such as the oceans, are compacted by overlying sediments and converted to sedimentary rocks. The
process of creating rock by compacting and cementing particles is called lithification. Sedimentary rocks
buried at sufficient depths (usually tens to hundreds of kilometers) are altered by heat, pressure, or
chemically active fluids and transformed into metamorphic rocks. Later, plate tectonics uplift may bring
these deeply buried rocks to the surface, where they, too, are subjected to weathering, producing new
sediment and starting the cycle again. You can see in Figure 6.14 that life processes play an important role
in the rock cycle by adding organic carbon to rocks. The addition of organic carbon produces rocks such as
limestone, which is mostly calcium carbonate (the material of seashells and bones), as well as fossil fuels,
such as coal. p. 116
Ch. 18
- To understand water as a necessity, as a resource, and as a factor in the pollution problem, we must
understand its characteristics, its role in the biosphere, and its role in sustaining life. Water is a unique
liquid; without it, life as we know it is impossible. Consider the following:
o Compared with most other common liquids, water has a high capacity to absorb and store heat. Its
capacity to hold heat has important climatic significance. Solar energy warms the oceans, storing
huge amounts of heat. The heat can be transferred to the atmosphere, developing hurricanes and
other storms. The heat in warm oceanic currents, such as the Gulf Stream, warms Great Britain and
Western Europe, making these areas much more hospitable for humans than would otherwise be
possible at such high latitudes.
o Water is the universal solvent. Because many natural waters are slightly acidic, they can dissolve a
great variety of compounds, ranging from simple salts to minerals, including sodium chloride
(common table salt) and calcium carbonate (calcite) in limestone rock. Water also reacts with
complex organic compounds, including many amino acids found in the human body.
o Water is the only common compound whose solid form is lighter than its liquid form. (It expands by
about 8% when it freezes, becoming less dense.) That is why ice floats. If ice were heavier than
liquid water, it would sink to the bottom of the oceans, lakes, and rivers. If water froze from the
bottom up, shallow seas, lakes, and rivers would freeze solid. All life in the water would die because
cells of living organisms are mostly water, and as water freezes and expands, cell membranes and
walls rupture. If ice were heavier than water, the biosphere would be vastly different from what it is,
and life, if it existed at all, would be greatly altered.
o Sunlight penetrates water to variable depths, permitting photosynthetic organisms to live below the
surface.
Questions to consider:
- Explain the processes of erosion and deposition.
- How do erosion and deposition compare and contrast?
- What role does water play in erosion and deposition?
- Explain how beach sand, that was once coral and sea shells, gets deposited on land.
- Why are rocks from oceans, rivers, and lakes smooth while those on land are not?
- Which is more absorbent, dry soil or wet soil? Why?
- Which erodes more easily after heavy rains – a desert or a rainforest? Why? How do you know?
- Explain how frost/ice wedging causes erosion.
- Describe how water, when mixed with acids, is able to dissolve rocks, particularly limestone.
- Describe how caves are formed.
- Explain how rust is formed and how it weakens the metal.
- Describe how acid rain dissolves metals (including buildings and statues).
- Explain the process of recrystallization, which is a form of deposition.
- How are cast and mold fossils formed?
- Explain how sea salt is “mined”.
- Explain the formation of geodes.
- The addition of salt to water will lower the freezing point of water. Explain what happens when water is
added to rock as it is becoming magma.
- Portland, Oregon; Ottawa, Ontario; and Venice, Italy are all at the same latitude but each has a very
different climate. Why?
- At noon on a hot summer’s day, why is the water at the beach cool, but the sand very hot?
- Explain where the energy from a hurricane comes from.
- Why do ponds have plants living on the bottom, but lakes do not?