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6430
  • OLP 2: The ocean and life in the ocean shape the features of Earth

    Many earth materials and biogeochemical cycles originate in the ocean. Many of the sedimentary rocks now exposed on land were formed in the ocean. Ocean life laid down the vast volume of siliceous and carbonate rocks. Sea level changes over time have expanded and contracted continental shelves, created and destroyed inland seas, and shaped the surface of land. Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean, and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents. The ocean is the largest reservoir of rapidly cycling carbon on Earth. Many organisms use carbon dissolved in the ocean to form shells, other skeletal parts, and coral reefs. Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

  • OLP 2.C

    Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.

  • OLP 2.E

    Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

OLP 2.C

Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.
OLP 2.C

 

 

 

Balanced and Unbalanced Forces

Forces acts on one particular object with both a strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object’s speed or direction of motion. For example, when the ocean is still in a particular area, the forces are balanced and the sand will remain on the beach. If the energy stored in waves is active and the waves are strong, the beach may experience erosion as the sand particles are pulled off shore. Depending on the strength of the waves, the erosion on a beach may be more or less severe.

The Force of Waves

 

Most ocean waves are caused by wind (see The Forces of Wind topic). The type of waves tend to change with seasonal changes in wind. For example, during the winter, waves on the northern shores of the Hawaiian islands can be very large. The force of these large winter waves pry sand and rocks from the shore and carry them into deeper waters. In contrast, small summer waves on the northern Hawaiian shores are gentle, but the force of them helps to return sand and rocks back to shore. The opposite is true of southern shores in Hawaiʻi, which tend to have higher swells in the summer than in the winter.

Waves are strong. The force of waves can carry people, plants, animals, and trash (Fig. 1). The force of waves can also cause dramatic change to the beach and shore. Large, storm waves can pull the sand from a beach! Small waves can slowly build up and washing away of sand on a beach.

 

 

 

 

Wave-Coast Interactions

The study of wave and beach interactions contributes to our understanding of the processes of erosion (loss) and accretion (buildup). Sand erosion is often a problem for property owners because it removes valuable property (Fig. 2). Sand accretion can also be a problem; for example, a sandbar can block boat channels, and sand deposits can fill harbors.

 

 

 

 

In an undisturbed coastal area, sand stored on the low-lying coastal plain is released to the beach as sea level rises. This allows the beach to maintain a wide sandy shoreline even as a sinking island or rising sea level causes the beach to migrates landward. However, the hardening of the shoreline, which is the construction of vertical seawalls and revetments to protect coastal lands from marine erosion, protects the immediate area for a limited time but ultimately causes erosion by preventing waves from accessing sandy reservoirs (Fig. 3).

 

 

Studies conducted at the University of Hawai‘i show that hardening the shoreline of Oʻahu has caused 10.7 miles of beach to narrow and 6.4 miles to be lost. This is ~24% of the 71.6 miles of originally sandy shoreline on Oʻahu. The loss of beaches not only negatively impacts human activities and property but also affects the environment by smothering local marine life with eroded sediment and causing sewage spills into nearshore waters. In order to save beaches, scientists recommend replenishing sand, keeping coastal areas free of hardened structures and requiring large setbacks of new development. See the example photo taken at central Kailua beach on Oʻahu, showing adjacent property lots with sufficient and insufficient setback (Fig. 4).

The main causes of coastal erosion are:

  1. High waves and currents
  2. Human impacts
  3. Sea level rise

 

 

Wave Erosion Vocabulary:

  • Accretion: the process of growth or increase, typically by the gradual accumulation of additional layers or matter
  • Erosion: the process of eroding or being eroded by wind, water, or other natural agents
  • Revetment: a retaining wall or facing of masonry or other material, supporting or protecting a rampart, wall, etc.
  • Seawall: a wall or embankment erected to prevent the sea from encroaching on or eroding an area of land
  • Swell: a slow, regular movement of the sea in rolling waves that do not break
  • Waves: a long body of water curling into an arched form and breaking on the shore

 

6406
  • OLP 2: The ocean and life in the ocean shape the features of Earth

    Many earth materials and biogeochemical cycles originate in the ocean. Many of the sedimentary rocks now exposed on land were formed in the ocean. Ocean life laid down the vast volume of siliceous and carbonate rocks. Sea level changes over time have expanded and contracted continental shelves, created and destroyed inland seas, and shaped the surface of land. Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean, and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents. The ocean is the largest reservoir of rapidly cycling carbon on Earth. Many organisms use carbon dissolved in the ocean to form shells, other skeletal parts, and coral reefs. Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

  • OLP 2.C

    Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.

  • OLP 2.E

    Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

OLP 2.C

Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.
OLP 2.C

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ACTIVITY: Source of Hawaiian Sand

Weathering and Erosion

Weathering is the process of breaking down Earthʻs surface into smaller peices. Weathering is often caused by wind, water, ice, plants, and changes in temperature.

 

Erosion is similar to weathering, but it also includes the movement of weathered pieces and their deposition. Erosion occurs through wind, running water, such as rivers, and even in the slow movement of ice in glaciers. Living organisms can also contribute to erosion. For example, plant roots can wedge inbetween cracks in rocks, and fish can break off peices of rock as they eat algae.

 

Both weathering and erosion can occur very quick, like during mudslides. Weathering and erosion can also be very slow, like in the formation of stream beds as water trickles through. We see examples of weathering and erosion every day—from cracks in the sidewalks, to sand at the beach, to rocks sliding down mountains (Fig. 1).

 

 

Biological organisms can also change the physical features of Earth. The science of biogeology explores the interactions between the living and non-living features of Earth.

The Different Sands of Hawaiʻi

The sand that makes up the beaches in Hawai‘i originates from a number of different sources. The main source of sand can often be determined by color. In Hawaiʻi, there are beaches of red, black, green, and white sand. Many beaches often have multiple types of sand as well as particles from other sources (like marine debris).

VOICE OF THE SEA: Saving Hawaii’s Beaches

 

Red, black, and green sands come from volcanic rock

 

Volcanic sand is formed by weathering and mechanical erosion. Red sand beaches are rare. They come from volcanic rock that is rich in iron. Kaihalulu beach on Maui is an example of a red sand beach (Fig. 2).

 

Obsidian black sand beaches form when lava enters the ocean and is rapidly cooled into black glass. The glass explodes due to the rapid cooling, and fragments are distributed onto the shoreline. Over time, these fragments become eroded by wave action into fine grains, producing the black sand of obsidian beaches—like those at Punalu‘u, Ho‘okena, and Kealakekua beaches on the island of Hawai‘i (Fig. 3). Other beaches may have black sand from erosion of volcanic rock, but they are not as uniformly dark as beaches formed primarily from obsidian glass.

 

Green sand beaches are also formed by weathering. The mineral olivine comes from volcanic rock, which erodes into sand grains to form green sand beaches (Fig. 4).

 

White sand comes from living organisms

 

White sands are primarily made from the small remnants of living things. White sand and is often made of calcareous algae and skeletons from coral or other animals that have calcium carbonate shells or structures (Fig. 5). White sand beaches are more common in locations near reef structures. The development of white sand takes time for the dynamic processes of mechanical and biological erosion (bioerosion) to occur. During mechanical erosion, coral fragments are broken off during storms or other disturbances. These fragments, along with animal shells and calcified algae, roll back and forth with the waves, slowly eroding into smaller and smaller particles that become sand. White sand can be found in places like Lanikai beach on O‘ahu.

Animals help form sand

 

Animals that dig into coral for food help to create sand through the process of bioerosion. For example, parrotfish (uhu) are considered important bioeroders on the reef (Fig. 6). They use their fused jaws to break off pieces of live coral in order to digest the algae that live in and around the coral tissues. In the process, parrotfish grind the coral skeleton and deposit it back on the reef as a waste product. Researchers estimate that parrotfish in Hawai‘i contribute up to 70% of the white sand on the beach. In addition, animals like boring sponges, worms, and bivalves, urchins, and fish also produce sand as a byproduct of grazing on coral.

Other animals that contribute to the creation of white sands include shelled animals that leave their shelled homes or spines behind when they die, such as snails, oysters, scallops, and urchins (Fig. 7). These structures roll with the waves and are slowly eroded into sand particles. Calcareous algae, like Halimeda (Fig. 8), and coralline algae, like the encrusting pink alga that cements reefs together, also leave behind their calcium carbonate structures that erode to become sand particles over time. In addition, herbivorous fishes may eat calcareous algae and deposit the remains as sand.

 

 

 

Weathering and Erosion Vocabulary

  • Bioerosion: the biological process of erosion due to grazing, boring organisms and other living organisms that break up the reef into smaller particles.
  • Biogeology: the study of the interactions between the living and non-living features of Earth.
  • Byproduct: a secondary result, unintended but inevitably produced, in doing or producing something else.
  • Deposition: the placement of something in a new location.
  • Calcium Carbonate: a white solid that occurrs naturally as chalk, limestone, marble, and calcite. It also makes up the shells or skeletons of many marine organisms, like oysters, urchins, coral, and calcareous algae.
  • Erosion: the breaking down and transport of material.
  • Mechanical erosion: erosion due to movement and wear and tear of material from wave action, wind, water transport, etc.
  • Obsidian: a hard, dark, glasslike volcanic rock formed by the rapid solidification of lava without crystallization.
  • Olivine: an olive-green, gray-green, or brown mineral occurring widely in basalt, peridotite, and other basic igneous rocks. It is a silicate containing various proportions of magnesium, iron, and other elements.
  • Sand: broken down rock or organic material that makes up beaches.
  • Weathering: the physical process of wind and precipitation breaking down rock into smaller particles.
6405
  • OLP 2: The ocean and life in the ocean shape the features of Earth

    Many earth materials and biogeochemical cycles originate in the ocean. Many of the sedimentary rocks now exposed on land were formed in the ocean. Ocean life laid down the vast volume of siliceous and carbonate rocks. Sea level changes over time have expanded and contracted continental shelves, created and destroyed inland seas, and shaped the surface of land. Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean, and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents. The ocean is the largest reservoir of rapidly cycling carbon on Earth. Many organisms use carbon dissolved in the ocean to form shells, other skeletal parts, and coral reefs. Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

  • OLP 2.C

    Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.

  • OLP 2.E

    Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast.

OLP 2.C

Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents.
OLP 2.C

[ct_terms tax_slug=ngss_performance_expectations tax_url=ess2-earth-s-systems-2]

[ct_terms tax_slug=curriculum_alignment tax_url=introduction-ocean-literacy-principles-olp-2]

ESS2: Earth’s System:
How and why is Earth constantly changing?

ESS2.A: Earth Materials and Systems: How do Earth’s major systems interact?

Learning goals by the end of grade 5: Earth’s major systems are the geosphere (solid and molten rock, soil, and sediments), the hydrosphere (water and ice), the atmosphere (air), and the biosphere (living things, including humans). These systems interact in multiple ways to affect Earth’s surface materials and processes. The ocean supports a variety of ecosystems and organisms, shapes landforms, and influences climate. Winds and clouds in the atmosphere interact with the landforms to determine patterns of weather. Rainfall helps shape the land and affects the types of living things found in a region. Water, ice, wind, living organisms, and gravity break rocks, soils, and sediments into smaller particles and move them around. Human activities affect Earth’s systems and their interactions at its surface.

ESS2.B: Plate Tectonics and Large-Scale System Interactions: Why do the continents move, and what causes earthquakes and volcanoes?

Learning goals by the end of grade 5: The locations of mountain ranges, deep ocean trenches, ocean floor structures, earthquakes, and volcanoes occur in patterns. Most earthquakes and volcanoes occur in bands that are often along the boundaries between continents and oceans. Major mountain chains form inside continents or near their edges. Maps can help locate the different land and water features where people live and in other areas of Earth.

ESS2.E: Biogeology: How do living organisms alter Earth’s processes and structures?

Learning goals by the end of grade 5: Living things affect the physical characteristics of their regions (e.g., plants’ roots hold soil in place, beaver shelters and human-built dams alter the flow of water, plants’ respiration affects the air). Many types of rocks and minerals are formed from the remains of organisms or are altered by their activities.

Ocean Literacy Principles

 

Principle 1: The Earth has one big ocean with many features.

Ocean Literacy Fundamental Concept: The ocean is the defining physical feature on our planet Earth—covering approximately 70% of the planet’s surface. There is one ocean with many ocean basins, such as the North Pacific, South Pacific, North Atlantic, South Atlantic, Indian, Southern, and Arctic. (OLP1a)

Ocean Literacy Fundamental Concept: Ocean basins are composed of the seafloor and all of its geological features (such as islands, trenches, mid-ocean ridges, and rift valleys) and vary in size, shape and features due to the movement of Earth’s crust (lithosphere). Earth’s highest peaks, deepest valleys and flattest plains are all in the ocean.  (OLP1b)

Principle 2: The ocean and life in the ocean shape the features of Earth.

Ocean Literacy Fundamental Concept: Many earth materials and biogeochemical cycles originate in the ocean. Many of the sedimentary rocks now exposed on land were formed in the ocean. Ocean life laid down the vast volume of siliceous and carbonate rocks (OLP2a)

Ocean Literacy Fundamental Concept: Erosion—the wearing away of rock, soil and other biotic and abiotic earth materials—occurs in coastal areas as wind, waves, and currents in rivers and the ocean, and the processes associated with plate tectonics move sediments. Most beach sand (tiny bits of animals, plants, rocks, and minerals) is eroded from land sources and carried to the coast by rivers; sand is also eroded from coastal sources by surf. Sand is redistributed seasonally by waves and coastal currents (OLP2c)

Ocean Literacy Fundamental Concept: Tectonic activity, sea level changes, and the force of waves influence the physical structure and landforms of the coast. (OLP2e)

These concepts will be explored in this unit through the following activities and investigations:

ACTIVITY: Source of Hawaiian Sand

 

ACTIVITY: Modeling Plate Movement