Earth and Space Science Notes
EARTH AND SPACE SCIENCE
LESSON 1: System Models - Faults and Earthquakes
Faults and Types of Faults
Faults play a crucial role in geology, helping us understand Earth's structure, tectonics, and surface processes.
They are fundamental features in the Earth’s crust, where rocks have undergone deformation due to stress, resulting in fractures or displacements along geological planes.
Studying faults helps in understanding earthquake hazards, resource exploration, and deciphering Earth’s history.
A fault is a fracture in the Earth’s crust along which movement has occurred. These movements can be horizontal, vertical, or a combination of both.
Faults are classified based on the relative movement of the rock on either side of the fracture and are characterized by various parameters, including the dip angle, strike direction, and sense of motion.
Types of Faults
Normal Fault:
The hanging wall (the block of rock above the fault plane) moves downward relative to the footwall (the block of rock below the fault plane).
Common at divergent plate boundaries where the Earth’s crust is stretching.
Reverse Fault (Thrust Fault):
The hanging wall moves upward relative to the footwall.
Typically occur at convergent plate boundaries where tectonic plates are colliding and undergoing compression.
Strike-Slip Fault:
The movement is primarily horizontal, with minimal vertical displacement.
The rocks on either side of the fault slide past each other horizontally. The San Andreas Fault in California is a famous example.
Transform Fault:
A type of strike-slip fault that forms the boundary between two tectonic plates.
They accommodate horizontal motion between the plates.
The motion is typically parallel to the fault’s strike.
Based on Geological Setting:
Plate Boundary Faults: Located at the boundaries of tectonic plates and play a significant role in plate tectonics. Examples include the San Andreas Fault (a transform fault) at the boundary between the Pacific and North American plates and the Himalayan Thrust Fault at the convergent boundary of the Indian and Eurasian plates.
Intraplate Faults: Occur within the interior of tectonic plates, away from plate boundaries. They are less common but can still generate significant seismic activity. An example is the New Madrid Seismic Zone in the central United States.
Based on Fault Geometry:
Dip-Slip Fault: The movement is primarily vertical along the fault plane. Normal and reverse faults are both types of dip-slip faults.
Strike-Slip Fault: Primarily involve horizontal movement along the fault plane. These faults can be further classified as right-lateral or left-lateral, depending on the direction of horizontal movement when facing the fault.
Oblique-Slip Fault: Combine both vertical (dip-slip) and horizontal (strike-slip) movements. These faults do not fit neatly into the categories of normal, reverse, or strike-slip.
Listric Fault: Has a curved fault plane that steepens with depth. This type of fault is often associated with extensional tectonics and can transition from normal faulting at the surface to a low-angle fault deeper within the Earth’s crust.
Key Characteristics of Faults
Faults are geological features characterized by fractures or zones of weakness in the Earth’s crust, along which movement has occurred. These fractures can vary in size and scale, and their characteristics provide valuable information about the history and dynamics of the Earth’s crust.
Classifications help geologists and seismologists understand the behavior and characteristics of faults in various geological settings, which, in turn, contributes to our understanding of tectonics, seismic hazards, and geological history.
The “Ring of Fire” is a horseshoe-shaped zone around the Pacific Ocean characterized by frequent earthquakes and volcanic activity, encompassing approximately 75% of the world’s active and dormant volcanoes and 90% of its earthquakes.
The Philippines is a seismically active region with numerous active faults, including the Philippine Fault Zone (PFZ), a major left-lateral strike-slip fault that traverses the archipelago, and notable segments like the Guinayangan, Masbate, and Central Leyte faults.
Earthquake Risk in the Philippines
The Philippines is located in the Pacific Ring of Fire, a region known for high seismic and volcanic activity.
The presence of active faults and trenches, like the Manila Trench and the Philippine Trench, contributes to the country’s earthquake and tsunami risk.
Provinces like Surigao del Sur, La Union, Benguet, Pangasinan, Tarlac, Pampanga, Ifugao, Davao Oriental, Nueva Vizcaya, and Nueva Ecija are considered at higher risk due to the presence of or their nearness to active faults.
Additionally, the historical occurrence of significant earthquakes in these areas highlights the need for ongoing monitoring and preparedness measures to mitigate potential hazards. Furthermore, it is essential for local governments and communities to implement strict building codes and conduct regular earthquake drills to ensure the safety and resilience of structures and populations in these vulnerable regions.
Assess a chosen location in the country, detailing its strengths, weaknesses, opportunities, and threats related to natural resources.
LESSON 2: Earthquakes
Objectives
Use the PHIVOLCS Fault Finder or other reliable information source to identify where the nearest fault system is located from their community and assess the risk of earthquakes to their local community.
Make models of fault scenarios to illustrate:
a. the epicenter of an earthquake from its focus,
b. the intensity of an earthquake from its magnitude,
c. how underwater earthquakes may or may not generate tsunamis.
Introduction to Earthquakes
Earthquake: The shaking of the Earth's crust as a result of the energy released by volcanic activity or shifting of rock layers from the Earth's interior.
Tectonic Earthquake: Occurs when rocks in the Earth's crust break due to the movement of plates.
Volcanic Earthquake: Caused by volcanic activity.
Focus and Epicenter
Focus (Hypocenter): The point within the Earth where faulting begins.
Epicenter: The point directly above the focus on the surface.
Seismic Waves
Energy released during an earthquake travels in seismic waves.
Body Waves: Travel through the Earth’s inner layers.
Surface Waves: Can only move along the surface of the planet.
Intensity
Measures the damage done on the surface and its effect on humans.
Helps determine the size of the area affected by the earthquake.
Usually measured in the Rossi-Forel Scale.
Rossi-Forel Scale of Earthquake Intensities
I: Hardly perceptible shock – felt only by an experienced observer under favorable conditions.
II: Extremely feeble shock – felt by a small number of persons at rest.
III: Very feeble shock – felt by several persons at rest. Duration and direction may be perceptible. Sometimes dizziness or nausea experienced.
IV: Feeble shock – felt generally indoors, outdoors by a few. Hanging objects swing slightly. Creaking of frames of houses.
V: Shock of moderate intensity – felt generally by everyone. Hanging objects swing freely. Overturning of tall vases and unstable objects.
VI: Fairly strong shock – general awakening of those asleep. Some frightened persons leave their houses. Stopping of pendulum clocks. Oscillation of hanging lamps. Slight damage to very old or poorly built structures.
VII: Strong shock – overturning of movable objects. General alarm; all run outdoors. Damage slight in well-built houses, considerable in old or poorly built structures, old walls, etc. Some landslides from hills and steep banks. Cracks in road surfaces.
VIII: Very strong shock – people panicky. Trees shaken strongly. Changes in the flow of springs and wells. Sand and mud ejected from fissures in soft ground. Small landslides.
IX: Extremely strong shock – panic general. Partial or total destruction of some buildings. Fissures in ground. Landslides and rockfalls.
Magnitude
The amount of energy released by an earthquake.
Uses the Richter Magnitude Scale that measures from 1-10.
Richter Magnitude Scale
1: Earthquake with M below 1 are only detectable when an ultra-sensitive seismometer is operated under favorable conditions.
2: Most earthquakes with M below 3 are the “hardly perceptible shocks” and are not felt. They are only recorded by seismographs of nearby stations.
3: Earthquake with M 3 to 4 are the “very feeble shocks” and only felt near the epicenter.
4: Earthquakes with M 4 to 5 are the “feeble shocks” where damages are not usually reported.
5: Earthquakes with M 5 to 6 are the “earthquakes with moderate strength” and are felt over wide areas; some of them cause small local damages near the epicenter.
6: Earthquake with M 6 to 7 are the “strong earthquakes” and are accompanied by local damages near the epicenters. First class seismological stations can observe them wherever they occur within the earth.
7: Earthquake with M 7 to 8 are the “major earthquakes” and can cause considerable damages near the epicenters. Shallow-seated or near-surface major earthquakes when they occur under the sea, may generate tsunamis. First class seismological stations can observe them wherever they occur within the earth.
8: Earthquake with M 8 to 9 are the “great earthquakes” occurring once or twice a year. When they occur in land areas, damages affect wide areas. When they occur under the sea, considerable tsunamis are produced. Many aftershocks occur in areas approximately 100 to 1,000 kilometers in diameter.
9: Earthquakes with M over 9 have never occurred since the data based on the seismographic observations became available.
Instruments Used to Detect Earthquakes
Seismograph
Laser Rangefinder
Geiger Counter
Extensometer
LESSON 3: Earthquakes and Tsunamis
Tsunamis can be triggered by earthquakes or subaqueous landslides.
Tsunami Wave Generation
Large magnitude subduction zone earthquakes can experience as much as meters ( feet) of crustal offset in the sea floor.
Large-scale subaqueous landslides can also create significant wave energy.
Tsunamis travel at speeds between and miles per hour across the open ocean, with wavelengths of about kilometers!
Ships in the open ocean cannot discern the waves as they pass by because of their extreme wavelength.
The transit speed of tsunamis is reduced in shallow water, and the wave height increases rapidly.
The largest tsunamis have historically emanated from the Pacific “Ring of Fire”, formed by thin oceanic plates being subducted beneath thicker continental crust.
Tsunamis arrive as a series of waves, separated by a few minutes to a few hours. The waves can last for up to three days.
LESSON 4: Earthquake and Tsunami Preparedness
Before the Shaking Starts
Know safe spots in each room: against inside walls, under sturdy tables, desks, or archways.
Identify danger spots: windows, mirrors, hanging objects, fireplaces, and tall, unsecured furniture.
Practice family drills and physically place yourself in safe locations, especially important for children.
Learn first aid and CPR.
Keep a list of emergency numbers.
Prepare a family emergency kit with supplies for at least 72 hours.
Know how to shut off gas, water, and electricity.
Keep breakables or heavy objects on bottom shelves.
Secure tall, heavy furniture that could topple, such as bookcases, cabinets, or wall units.
Secure the water heater and appliances.
Secure hanging plants and heavy picture frames or mirrors (especially over beds).
Put latches on cabinet doors to hold closed during shaking.
Keep flammable or hazardous liquids such as paints, pest sprays, or cleaning products in the garage or outside shed.
Check chimneys, roofs, walls, foundations for structural condition.
Maintain emergency food, water and other supplies, including flashlight, a portable battery-operated radio, extra batteries, medicines, first aid kit and clothing.
During the Shaking
If indoors, stay there. Drop, cover, and hold. Get under a desk or table and hang on. Alternately, you can stand in an archway or corner.
If outdoors, get into an open area away from trees, buildings, walls, and power lines.
If in a high-rise building, stay away from windows and outside walls. Get under a table. Do not use the elevators.
If driving, pull your car to the side of the road and stop. Avoid overpasses or power lines. Remain inside until the shaking is over.
If in a crowded public place, do not rush for the doors. Move away from display shelves containing objects that may fall.
In all instances, drop, cover, and hold; protect your head as much as possible.
After the Shaking Stops
Stay calm and check for injuries. Apply first aid if qualified. Do not move any seriously injured individuals unless they are in immediate danger.
Check for fires, gas and water leaks, and damaged electrical wiring or sewer lines.
If you smell gas, do not use matches, candles, etc., and do not operate electrical switches.
Check the building for cracks and damage, including roof, chimneys, and foundation. If you suspect there is serious damage, turn off all utilities and leave the building.
Check food and water supplies. Emergency water may be obtained from water heaters, melted ice cubes, toilet tanks, and canned vegetables.
Seek sources of uncontaminated water. In an emergency, purify water by straining through a paper towel or several layers of clean cloth and by boiling vigorously for at least six minutes.
Do not use BBQ’s, camp stoves, or unvented heaters indoors.
Do not flush the toilet if the sewer line is damaged.
Do not use the telephone unless there is a severe injury or fire to report.
Turn on your portable radio for instructions and news reports, and cooperate fully with public safety officials.
Keep Disaster Response Routes clear for emergency vehicles.
LESSON 5: The Sun’s Influence on Earth
Objectives
Demonstrate how the tilt of the Earth relative to its orbit around the Sun affects the intensity of sunlight absorbed by different areas of Earth over a year.
Discuss how energy from the Sun interacts with the layers of the atmosphere.
Account for the occurrence of land and sea breezes, monsoons, and intertropical convergence zone (ITCZ).
Air Temperature and Atmospheric Layers
Warm air rises because gas molecules are able to move freely and if they are uncontained, as they are in the atmosphere, they can take up more or less space.
When gas molecules are cool, they are sluggish and do not take up as much space. With the same number of molecules in less space, both air density and air pressure are higher.
When gas molecules are warm, they move vigorously and take up more space.
Air density and air pressure are lower.
Warmer, lighter air is more buoyant than the cooler air above it, so it rises. The cooler air then sinks down, because it is denser than the air beneath it. This is convection.
The property that changes most strikingly with altitude is air temperature. The atmosphere is divided into layers based on how the temperature in that layer changes with altitude, the layer's temperature gradient.
The four main layers of the atmosphere have different temperature gradients, creating the thermal structure of the atmosphere.
Most of the important processes of the atmosphere take place in the lowest two layers: the troposphere and the stratosphere.
Troposphere
The temperature of the troposphere is highest near the surface of the Earth and decreases with altitude. On average, the temperature gradient of the troposphere is per m ( per ft.) of altitude.
Earth's surface is a major source of heat for the troposphere, although nearly all of that heat comes from the Sun. Rock, soil, and water on Earth absorb the Sun's light and radiate it back into the atmosphere as heat.
The air in the troposphere does a lot of mixing. This mixing causes the temperature gradient to vary with time and place. The rising and sinking of air in the troposphere mean that all of the planet's weather takes place in the troposphere.
Sometimes there is a temperature inversion, air temperature in the troposphere increases with altitude, and warm air sits over cold air. Inversions are very stable and may last for several days or even weeks.
Stratosphere
In the stratosphere, temperature increases with altitude.
The direct heat source for the stratosphere is the Sun. The air in the stratosphere is stable because warmer, less dense air sits over cooler, denser air. As a result, there is little mixing of air within the layer.
The ozone layer is found within the stratosphere between 15 to 30 km (9 to 19 miles) altitude.
The ozone layer is extremely important because ozone gas in the stratosphere absorbs most of the Sun's harmful ultraviolet (UV) radiation. Because of this, the ozone layer protects life on Earth.
Mesosphere
Temperatures in the mesosphere decrease with altitude.
Because there are few gas molecules in the mesosphere to absorb the Sun's radiation, the heat source is the stratosphere below. The mesosphere is extremely cold, especially at its top, about ().
The air in the mesosphere has extremely low density: % of the mass of the atmosphere is below the mesosphere. As a result, air pressure is very low.
Thermosphere and Beyond
Within the thermosphere is the ionosphere. The ionosphere gets its name from the solar radiation that ionizes gas molecules to create a positively charged ion and one or more negatively charged electrons.
At night, radio waves bounce off the ionosphere and back to Earth. This is why you can often pick up an AM radio station far from its source at night.
The Van Allen radiation belts are two doughnut-shaped zones of highly charged particles that are located beyond the atmosphere in the magnetosphere.
When massive solar storms cause the Van Allen belts to become overloaded with particles, the result is the most spectacular feature of the ionosphere - the nighttime aurora.
LESSON 2B: Interactions in the Atmosphere - Land and Sea Breezes, Monsoons, and ITCZ
Sea Breeze
During the day, both the sea and the land surface are heated up by the sun.
The sea heats up slower than the land because it has a much higher heat capacity.
The temperature over the land surface increases, in turn, heating up the surrounding air.
Expansion occurs in the less dense warm air, and an area over the land having low pressure is developed.
At the same time on the top of the sea, a high-pressure area develops.
Due to the difference in pressure, air flows from the high pressure over the sea to the low pressure over the land. This flow of air from the sea to the land is termed the sea breeze.
The sea breeze is more prevalent on warm sunny days during the spring and summer.
Land Breeze
This process takes place for the duration of the night and the above-mentioned process gets reversed.
Both, the land and the sea start cooling down when the sun sets.
As the heat capacity of the land is different from the sea, it cools down quicker.
Thus, a low-pressure situation develops over the sea as the temperature above it is higher when compared to the land.
Due to this, the air flows from the land to the sea, which is termed the land breeze.
Land breeze can occur at any time of year but is more prevalent during the fall and winter seasons when water temperatures are still fairly warm and nights are cool.
Amihan and Habagat in the Philippines
Amihan and Habagat refer to the two kinds of winds and seasons that occur in the country every year.
Amihan is known as the Northeast monsoon, while Habagat is known as the Southwest monsoon.
A monsoon is a seasonal rain and wind pattern.
Amihan: A cool and dry northeast wind coming from Siberia and China and blows down to Southeast Asia.
Habagat: The southwest wind characterized by frequent heavy rainfall and humid weather.
Inter-Tropical Convergence Zone (ITCZ)
The ITCZ (Intertropical Convergence Zone) play an important role in the global circulation system and is also known as the Equatorial Convergence Zone or Intertropical Front.
It is a basic low-pressure belt encircling Earth near the Equator. It is a zone of convergence where the trade winds meet.
ITCZ is caused by the convergence of northeast and southeast trade winds in the area encircling Earth near the Equator.
It appears as a band of clouds consisting of showers, with occasional thunderstorms, that encircles the globe near the equator due to the convergence of the trade winds.
Impacts of ITCZ on the Weather
Affects rainfall in the equatorial region due to the variation of location resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes.
Longer-term changes result in severe droughts or flooding.
Helps in the formation of cyclones because it is a zone of wind change and speed.
LESSON 6: The Sun's Influence on Earth - Seasons in the Philippines
Introduction to Seasons
Seasons and the Sun: Review the video and complete the KWL chart.
Factors Influencing Seasons
Many people have believed that the seasons were the result of the changing distance between Earth and the Sun.
Although Earth's orbit around the Sun is an ellipse, its distance from the Sun varies by only about 3%. That's not enough to cause significant variations in the Sun's heating.
The seasons are actually caused by the 23.5° tilt of Earth's axis.
In June the Northern Hemisphere