Carbonate Petrography

Carbonate petrography is the study of limestones, dolomites and associated deposits under optical or electron microscopes greatly enhances field studies or core observations and can provide a frame of reference for geochemical studies.

25 strangest Geologic Formations on Earth

The strangest formations on Earth.

What causes Earthquake?

Of these various reasons, faulting related to plate movements is by far the most significant. In other words, most earthquakes are due to slip on faults.

The Geologic Column

As stated earlier, no one locality on Earth provides a complete record of our planet’s history, because stratigraphic columns can contain unconformities. But by correlating rocks from locality to locality at millions of places around the world, geologists have pieced together a composite stratigraphic column, called the geologic column, that represents the entirety of Earth history.

Folds and Foliations

Geometry of Folds Imagine a carpet lying flat on the floor. Push on one end of the carpet, and it will wrinkle or contort into a series of wavelike curves. Stresses developed during mountain building can similarly warp or bend bedding and foliation (or other planar features) in rock. The result a curve in the shape of a rock layer is called a fold.

Where does energy in U.S come from? [Guest Article]

From burning firewood to using electricity from renewable sources, the home energy landscape has drastically changed over the last 150 years. This article and infographic explore the history of energy use and what the sustainable future may look like.

We no longer have to gather firewood for our wood-burning stoves to keep us warm at night, but there are a variety of energy sources used in each home. Most homes in the U.S. run on either electricity or natural gas, or a combination of both, but homeowners may also employ solar panels or even residential wind-powered solutions too. 

Looking at the charts below, you can see that energy consumption has grown significantly each year and in 2018, it hit an all-time high. However, you’ll notice some changes in the way we use each energy source. Coal is the only energy source below that has suffered a decline and renewable energy has recently surpassed nuclear energy. As new technologies are developed, we are finding new ways to meet the increased energy demand. The future of energy consumption will look very different than it does today.

home energy use infographic

Where does energy in US come from?
By no surprise, oil has been the largest and most popular source of energy. Since the 1950s, oil and natural gas were used to heat homes. Now in 2020, you know that petroleum is used for many other reasons and industries, from powering our cars to packaging products in plastic. 

Although coal was another popular source of energy, it has been on the decline for the last few decades. It’s less efficient than other sources and negatively impacts the environment. To answer that problem, the U.S. has been investing in renewable energy sources. Wind, solar, and geothermal energy are proving to be great resources for a clean future.

Are renewables the future?
Although only 11% of U.S. energy production comes from renewable sources, it is expected to grow. Solar, wind, and geothermal technology energy are three of the top sources for renewable energy. Among those, wind is the fastest growing and judging from the production map, it has wide geographic potential as well. Geothermal energy, which uses underground temperatures to transfer energy, is becoming a popular alternative for home heating and cooling. Of course, residential solar panels are gaining wide adoption as well. As renewable energy options become more available, the energy consumption landscape is likely to move toward a more sustainable future. 

This infographic from The Zebra walks through the history of energy use, where energy is produced, and what the future of energy may look like.
Author bio: Amanda Tallent is a writer who covers everything from business to lifestyle. She creates content to help people live more informed and confident lives. 
Want to write guest blog for us? See guidelines here

Factors Controlling the Shape of a River Delta

What is a Delta?
A delta is an accumulation of sediments at the mouth of a river that may consist of a network of distributary channels, wetlands, bars, tidal flats, natural levees and beaches that typically shift from on location to another. Delta shape is dependent of dominant current conditions where the mouth of the river: tide-, sea wave-, and storm-dominated.

Lena River Delta, Siberia.
Factors that control the shape of a River Delta? 

River deltas around the world are very different. The shape of a river delta is controlled by a variety of factors including:
• the volume of river discharge.
• the volume of sediment being deposited in a delta region.
• vegetation cover in delta regions capable of trapping sediments.
• tidal range conditions where the river enters the ocean.
• storm-related climate and oceanographic conditions.
• coastal geography (mountains or plains) in coastal regions.
• human activity is now a dominant factor influencing the shape of river deltas.

Yellow River Delta, China
Nile River Delta, Egypt.
River deltas like the Amazon and Indus Rivers discharge into the ocean where a high tidal range influence flow into and out of the mouth of the rivers. Some river delta region are highly effected by erosion effects of storms and high wave energy. Infrequent but intense superstorms impact the shape of deltas and shoreline, such as the impact of hurricanes on the Gulf Coast.

Indus River Delta, Pakistan

Human activity is responsible for the irregular shape of the Birdfoot Delta on the Mississippi River created by the constant dredging to keep shipping channels clear. The construction of dams and diversion of water out of the Colorado River has essentially shut of the supply of water and sediment to the Colorado River Delta in the Gulf of California.

The Mississippi Birdfoot Delta is largely controlled by Human activities
Changes to Mississippi River Delta over the last 4000 years ago.
A river no more. Very little water makes it to the Colorado River Delta

Thanks to Dr. Phil Stoffer for assisting in publishing this article.

Designing Buildings to Reduce the Impact of Earthquakes

Earthquakes rip through our cities, with seismic waves that tear down our buildings and take away lives in the process. Just two years ago, in September of 2017, a 7.1 earthquake thundered throughout Mexico City and killed nearly 230 people.

The main cause of damage isn’t from the earthquake but from the collapsing structures. Historical and pre-earthquake safe buildings are not equipped to shield themselves from these natural disasters, leading to loss of lives and immense costs.
How Earthquakes Wreak Havok
On average, collapsing buildings cause $2.1 billion in damage and 10,000 deaths a year. Let’s analyze how earthquakes damage manmade structures.

The shockwaves from earthquakes force horizontal pressure on buildings. Without the right structure to divert this energy away from the building, they collapse—killing the people inside of them. That’s because buildings are unable to handle side forces. Although they’re able to handle vertical forces, earthquakes attack the core of the building. The horizontal forces strike the columns, floors, beams, and connectors that hold them together—rupturing support frames.

How to Make a Building Earthquake-Proof
There are many methods that engineers use to make structures more earthquake-proof, they make improvements to the foundation, structure, material flexibility as well as preventing waves from hitting the buildings. Let’s examine the methods used to help buildings resist this deadly force. For a visualization of how these methods work check out the visuals at earthquake-proof visual by BigRentz.

1. Build A Flexible Foundation
One way to prevent seismic waves from traveling throughout a building is to use flexible pads made of steel and rubber to hold the building's foundation. In this manner, the pads “lift” the building above ground and absorb the earthquakes’ shocks.

2. Damping

Engineers also use shock absorbers (similar to the ones you find in cars) for earthquake resistant buildings. These fixtures help reduce the magnitude felt from the shockwaves for the building. They’re also responsible for slowing down the life-threatening movement when buildings sway after a quake.

To accomplish this, geological engineers use:
  • Vibrational Control Devices
By placing dampers between a column and a beam at each building level, they use pistons and oil to convert the motion into heat. The heat absorbs the shocks felt from the earthquake.
  • Pendulum Power
This method is used primarily in skyscrapers. Engineers use a large weight and hydraulics that move opposite of the earthquake’s motion to help reduce the effects of any seismic shocks that hit the building. 3. Shield Buildings from Vibrations
Concrete and plastic rings are built underneath three feet beneath the building in expanding rings. These rings are sometimes called, “seismic invisibility cloaks” because they keep waves from reaching the building. These rings channel shockwaves so that they move to the outer circles and divert away from the building. 4. Reinforce the Building’s Structure
Shear walls and cross braces help shift earthquake movement away to the foundation. Horizontal frames are also useful, as they redistribute forces to the building’s columns and walls. Lastly, moment-resisting frames help keep joints rigid, simultaneously allowing the structure to bend for safety. 5. Use Resistant Materials
It’s vital to note that the building materials you use have a huge effect on a building’s stability. Two of the best materials for earthquake-resistance are structural steel and wood. There are also innovative materials that are being incorporated into structures like bamboo and memory alloy (flexible but returns to its shape easily).

With the right geological engineering practices, we can make cities safer from unpredictable earthquakes. Many cities have implemented earthquake-safe codes and requirements for new construction. Although making structures completely earthquake-proof is difficult to achieve—the goal is to keep buildings standing tall and people inside them safe.

Happy New Year (2019) from Learning Geology Team

Guest Blog: How Speleothems Are Used To Determine Past Climates?

About author: Alex Graham is an undergraduate student at University of Newcastle, Australia. He is interested in Geology as a whole but his major interests include fluvial processes, karst systems and ocean science. During his visit to New Zealand, he has obeserved the glow worms in Waitomo Caves and spelunking in Nikau Caves.

Speleothems, more commonly known as stalactites or stalagmites, consist of calcium carbonate (calcite or aragonite) crystals of various dimensions, ranging from just a few micrometers to several centimetres in length, which generally have their growth axis perpendicular to the growth surface. Speleothems are formed through the deposition of calcium carbonate minerals in karst systems, providing archives of information on past climates, vegetation types and hydrology, particularly groundwater and precipitation. However, they can also provide information on anthropogenic impacts, landscape evolution, volcanism and tectonic evolution in mineral deposits formed in cave systems.

Stalagmite Formation
Rainfall containing carbonic acid weathers the rock unit (generally either limestone or dolomite) and seeps into the cracks, forming caverns and karst systems. The groundwater, percolating through such cracks and caverns, also contains dissolved calcium bicarbonate. The dripping action of these groundwater droplets is the driving force behind the deposition of speleothems in caves.
Core drilling of an active stalagmite in Hang Chuot cave.
Speleothems are mainly studied as paleoclimate indicators, providing clues to past precipitation, temperature and vegetation changes over the past »500,000 years. Radioisotopic dating of speleothems is the primary method used by researchers to find annual variations in temperature. Carbon isotopes (d^13C) reflect C3/C4 plant compositions and plant productivity, where increased plant productivity may indicate greater amounts of rainfall and carbon dioxide absorption. Thus, a larger carbon absorption can be reflective of a greater atmospheric concentration of greenhouse gases. On the other hand, oxygen isotopes (d^8O) provide researchers with past rainfall temperatures and quantified levels of precipitation, both of which are used to determine the nature of past climates.

Stalactite and stalagmite growth rates also indicate the climatic variations in rainfall over time, with this variation directly influencing the growth of ring formations on speleothems. Closed ring formations are indicative of little rainfall or even drought, where-as wider spaced ring formations indicate periods of heavy rainfall or flooding. These ring formations thus enable researchers to potentially predict and model the occurrence of future climatic patterns, based off the atmospheric signals extrapolated from speleothems. Researchers also use Uranium –Thorium radioisotopic dating, to determine the age of speleothems in karst formations. Once the layers have been accurately dated, researchers record the level of variance in groundwater levels over the lifetime of the karst formation. Hydrogeologists specialise in such areas of quantitative research. As a result, speleothems are widely regarded as a crucial geological feature that provide useful information for researchers studying past climates, vegetation types and hydrology.

Want to write guest blog for us? See guidelines here

10 of the Best Learning Geology Videos of 2017

Following are the best videos of 2017.
Some of the videos are part of our Live Virtual Field Tours project and Video Lecture Series while some videos were reposted by us.

1. Live from Kamokuna Ocean Entry, Big Island of Hawaii 

2. Live from Tucson Gem Show, Tucson, Arizona


3. The landslide of Maierato, Vibo Valentia, Calabria, Italy 

4. A double terminated Quartz being pulled from a pocket in the Alps. 

5. An incredible footage of a Flash flood

6. Live from Kaibab Limestone, South Rim, Grand Canyon


7. Earthquakes and the Richter scale with Fabiana from Geologia da Terra

8. Learn all about Actinolite with Chad keel

9. Soil Erosion 

10. Live from Mount Hood with Andrew Dunning of BetterGeology

Huge thanks to all who contribute videos to us and thanks to everyone for watching! :)

Want to contribute? Read guidelines here.

Basics of Basin Analysis

·         A sedimentary basin is an area in which sediments have accumulated during a particular time period at a significantly greater rate and to a significantly greater thickness than surrounding areas.

·         A low area on the Earth’s surface relative to surroundings e.g. deep ocean basin (5-10 km deep), intramontane basin (2-3 km a.s.l.)

·         Basins may be small (kms2) or large (106+ km2)

·         Basins may be simple or composite (sub-basins)

·         Basins may change in size & shape due to:
1.      erosion

2.      sedimentation
3.      tectonic activity
4.      eustatic sea-level changes
·         Basins may overlap each other in time

·         Controls on Basin Formation

1.      Accommodation Space,

a.       Space available for the accumulation of sediment
b.      T + E = S + W T=tectonic subsidence E= Eustatic sea level rise S=Rate of sedimentation W=increase in water depth
2.      Source of Sediment
a.       Topographic Controls
b.      Climate/Vegetation Controls
c.       Oceanographic Controls (Chemical/Biochemical Conditions)

·         The evolution of sedimentary basins may include:

1.      tectonic activity (initiation, termination)

2.      magmatic activity
3.      metamorphism
4.      as well as sedimentation
·         Axial elements of sedimentary basins:

1.      Basin axis is the lowest point on the basement surface

2.      Topographic axis is the lowest point on the depositional surface
3.      Depocentre is the point of thickest sediment accumulation

·         The driving mechanisms of subsidence are ultimately related to processes within the relatively rigid, cooled thermal boundary layer of the Earth known as the lithosphere. The lithosphere is composed of a number of tectonic plates that are in relative motion with one another. The relative motion produces deformation concentrated along plate boundaries which are of three basic types:

1.      Divergent boundaries form where new oceanic lithosphere is formed and plates diverge. These occur at the mid-ocean ridges.
2.      Convergent boundaries form where plates converge. One plate is usually subducted beneath the other at a convergent plate boundary. Convergent boundaries may be of different types, depending on the types of lithosphere involved. This result in a wide diversity of basin types formed at convergent boundaries.
3.      Transform boundaries form where plates move laterally past one another. These can be complex and are associated with a variety of basin types.

·         Many basins form at continental margins.
Using the plate tectonics paradigm, sedimentary basins have been classified principally in terms of the type of lithospheric substratum (continental, oceanic, transitional), the position with respect to a plate boundary (interplate, intraplate) and the type of plate margin (divergent, convergent, transform) closest to the basin.

·         Plate Tectonic Setting for Basin Formation

1.      Size and Shape of basin deposits, including the nature of the floor and flanks of the basin

2.      Type of Sedimentary infill
·         Rate of Subsidence/Infill

·         Depositional Systems
·         Provenance

·         Texture/Mineralogy maturity of strata

3.      Contemporaneous Structure and Syndepositional deformation

4.      Heat Flow, Subsidence History and Diagenesis

·         Interrelationship Between Tectonics - Paleoclimates - and Eustacy

1.      Anorogenic Areas------>

·         Climate and Eustacy Dominate

2.      Orogenic Areas--------->

Sedimentation responds to TectonismPlate Tectonics and Sedimentary Basin


SB = Suture Belt
RMP = Rifted margin prism
S C = Subduction complex
FTB = Fold and thrust belt
RA = Remnant arc
Wilson Cycle
about opening and closing of ocean basins and creation of continental crust.

Structural Controls on Sedimentary Systems in Basins Forming:

Stage 1: Capacity < Sediment

Fluvial sedimentation

Stage 2: Capacity = Sediment

Fluvial lacustrine Transition

Stage 3: Capacity > Sediment

Water Volume > excess capacity
Shallow-water lacustrine sedimentation

Stage 4: Capacity >> Sediment

Water volume = excess capacity
Deep-water lacustrine sedimentation

Stage 5: Capacity > Sediment

Water volume < excess capacity
Shallow-water lacustrine sedimentation     
Contributed by:

Rehan.A Farooqui
M.Sc Geology,,
University of Karachi.