Changes in Eccentricity (Orbit Shape) of Earth

Changes in Obliquity (Tilt) of Earth

Axial precession of Earth

Sheath Folds

Evolution of different coastal systems with time

36 Years into 3.8 Seconds

In this animated GIF, you can see the changes over time in this river course. This is near Pucallpa, Peru. Here, 36 years of change are condensed into 3.8 seconds.

 

Effect of drainage density on the hydrograph

Classification of river deltas

Crystallography Rotoinversion Projection

Type-2 Superposed Folding Using Analogue Modelling

Apsidal Precession

 

Planets orbiting the Sun follow elliptical (oval) orbits that rotate gradually over time (apsidal precession). The eccentricity of this ellipse, as well as the rate of precession, is exaggerated for visualisation. (Source: Wikipedia)

Rotation Speed and Axial Tilts of the Planets in Our Solar System

 

Dr. James O’Donoghue, a Planetary at NASA Goddard created a brilliant animation of the planets in our solar system. Using NASA imagery for each planet, O’Donoghue plotted the exact rotation periods (in hours and days) and the angle at which they rotate (axial tilt).

India's Journey

India's journey from 220 million years ago to present time. The GIF below shows how India has travelled from southern hemisphere to northern hemisphere and collided with Asia.

Copyright: Earth Science Hub (The GIF is made using Ancient Earth Globe)

"Oceanic Rainforest" - Why and How we need to save them?

  Saving the Rainforest of the Ocean

--Arindam Biswas

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Sometimes called rainforests of the sea, shallow coral reefs form some of Earth's most diverse ecosystems. They are fragile, partly because they are sensitive to water conditions. There are uplifted reefs also and they form a kind of marine terrace found in intertropical regions as a result of biological activity, shoreline advance and accumulation of reef materials. The formation of these platforms is controlled by changes in environmental conditions and by tectonic activity during recent geological times. Changes in climatic conditions have led to eustatic sea-level oscillations and isostatic movements of the Earth's crust, especially with the changes between glacial and interglacial periods.

Source: Hello Travel

Topographic and hydrographic information are basic elements in studies of nearshore geomorphology, hydrology, and sedimentary processes. This information includes both longterm and short-term changes taking place along the coast; which includes beach profiles, and changes due to erosion (Klemas, 2009). Remote sensing from satellites is an efficient and cost-effective approach to carry out the study. While remote sensing cannot provide the level of detail and accuracy at a single point than a field survey, the statistical power for inferring large scale patterns benefits in having complete areal coverage. Remote sensing imagery in the visible wavelengths is commonly used to perform mapping on coral reefs, utilising multispectral and hyperspectral data, acquired by airborne or satellite-based sensors. Both spatial and spectral resolutions help discriminate various mapping objective, from geomorphic zones (e.g., fore reef, reef crest) to benthic community cover (e.g., coral on reef matrix, algae and coral on rubble).  

Remote sensing covers many technologies, from satellites to airborne sensors, unmanned aerial systems, boat-based systems, and autonomous underwater vehicles. Using available remote sensing technologies for coral reef mapping, the extent of the reef can be studied routinely. Apart from mapping only, the rugosity, macroalgal matters, and bleached corals present in the colony can also be studied.  

A fire coral before (left) and after (right) bleaching. (Source: Mongabay)

Remote sensing techniques are also used to identify the proxy for various environmental parameters, such as estimation of water attenuation as a proxy for water depth, turbidity for sedimentation, algal bloom for pollution, and sea surface temperature for thermal stress....... To read the full story click here.

Time Transition View of Aral Sea

© Earth Science Hub (Made using Google Earth Photos)

Time transition view of the Aral Sea from 1985 to 2020. It is clearly visible that the impact of climate change is an inevitable fact.

Unified Geologic Map of the Moon

Source: MRCTR GIS LAB/Planetary Data System/ASTRO PEDIA/ NASA/USGS

How Earth is retaining its magnetic field?

Image Source: Today I Found Out

First of all, the Earth shows it's magnetic field because of it's internal geodynamic nature. And it is believed that Earth's outer core is responsible for this kind of behavior. Unlike the mineral-rich crust and mantle, the core is made almost entirely of metals. Along with iron (Fe), silicon (Si) is also found at Earth’s core whose thermal conductivity has an impact on Earth’s thermal structure, evolution, and dynamics, as it controls the magnitude of thermal and compositional sources required to sustain the internal geodynamo of Earth. Scientists have directly measured the thermal conductivity of both solid Fe and Fe-Si alloys up to 144 GPa and 3300 K. 15 at% Si alloyed in Fe significantly reduces its conductivity by almost 2 folds at 132GPa and 3000 K. At similar pressure-temperature conditions, an outer core with 15 at% Si would have a conductivity of about 20 W m^-1 K^-1, which is lower than pure Fe. This suggests that a lower minimum heat flow, around 3TW, across the core-mantle boundary than previously expected, and thus less thermal energy needed to operate the geodynamo.

🔖 To know more about this research Click here.

Anthropogenic Seismic Noise & COVID-19

Reduction of anthropogenic seismic noise due to COVID-19 lockdown

                                                                                                                                  -- Sandro Chatterjee

The Planet Earth is still trying its best to get rid of the unwanted guest, COVID-19. The impact of the virus is going to have a prolonged effect on the history of mankind. The down falling economies, joblessness, death of an entire generation are the harshest truth to stand with. But as the earth already refused to surrender in this battle vs. COVID -19, scientists all around the globe are looking for every positive impact in the upcoming days due to this deadly virus and the positive effects are now being signaled by the pulse of a seismometer.

The lack of human activities due to this prolonged lockdown caused human linked vibrations to be decreased by 50% between March and May 2020. The quiet period caused by the increasing social distancing, closure of industries, pubs, hotels, stadiums, and movies is the longest and most pronounced quiet period of Seismic noise ever recorded. The research work, led by Royal Observatory of Belgium and Imperial College London shows the dampening effects are most prominent in the densely populated areas. The quietness and the decreased human-generated noise are helping the researchers to accurately differentiate between natural and human seismic noises and are allowing them to detect previously concealed earthquake signals. The study also found the signatures of this lockdown measure on sensors buried hundreds of meters under the ground in remote areas. Researchers are eager to name this quiet period as “Anthropause”, as the anthropogenic activities are minimal and are the main causes to create this historical period. To read the full story Click Here.

The reduced anthropogenic noise in Brussels, Belgium after lockdown (source: Royal Observatory of Belgium)

Photography for Geoscientists

Why a Geologist Should Know The Basics of Photography

--Arindam Biswas

We, the Geologists are trained to observe and record the world around us. The simple use of a hammer, clinometer compass, hand lens, GPS, and notebook can help us to solve the mystery hidden within the rocks. Often, we click and use various photographs to unearth these mysteries. But do we really know how these photographs are taken? Or the proper use of a camera to take the best shots? Nowadays, with the advent of good mobile cameras, we click numerous photos during our field works but, if you notice carefully, most of those photos lack the basic requirements to be a good photograph. 

A camera is one of the most important tools for a geologist. When supported by proper knowledge of photography it can help us unravel the processes that shaped the landscape around us both at present and past times. Any geologist in the world needs to use a camera or a photograph for a better understanding of the processes going on and under the Earth’s surface. Even while using Google Earth, one is using a set of photos unknowingly to find features of their interest. So, as Geologists, we must know how things are working when someone is using a camera or a photograph.

I am not an expert in clicking photographs but I do understand the necessity of this valuable skill. So, here I am sharing my knowledge to make all my geologist friends aware of this valuable skill.

To be a useful photographer one must know a few things like how a camera works, how to compose the perfect frame and a little bit of post-processing knowledge. To read the full article click here.

Here these fractures in the ice are leading your eyes to the end of the horizon automatically. You do not have to put the effort to move your eyes from one point to another. (Image source: www.oreilly.com)

Earth's Plate Tectonics Began Over 3.2 Billion Years Ago

Paleomagnetic evidence for modern-like plate motion velocities at 3.2 Ga

by  Alec R. Brenner et al.

An artistic cross-section through forming Earth's crust approximately 3-4 billion years ago. Image credit: Alec R. Brenner

Plate tectonics has been the dominant surface geodynamical regime throughout Earth’s recent geological history. One defining feature of modern plate tectonics is the differential horizontal motion of rigid lithospheric plates. The physiography and composition of Earth’s modern crust bear evidence for plate tectonic or “mobile-lid” processes including subduction, collisional orogeny, rifting, and ocean spreading. The case for the Archean Earth [4.0 to 2.5 billion years (Ga) ago] is not so clear. The surviving Archean crust consists of ~35 cratons, most with characteristic architecture of rounded granitoid intrusive domes rimmed by steeply dipping greenstone keels. The composition of extant Archean crust is substantially more mafic than modern oceanic crust, with a high fraction of ultramafic rocks such as komatiites. These structural and compositional differences have led to a number of proposals that the Archean crust was constructed by exotic processes, including plume tectonics, sagduction/drip tectonics, and a vertically overturning lithosphere. Since some of these processes are difficult to reconcile with plate mobility, alternative geodynamical regimes have been proposed for the Archean Earth, including stagnant-lid and sluggish-lid modes in which the lithosphere was rendered immobile, or at least slowed, due to decoupling from the asthenosphere under elevated geothermal gradients. Other studies argue for a uniformitarian model of the Archean Earth, in which some variant of modern plate tectonics was in operation at least locally throughout Earth history. Complete understanding of the Archean lithosphere, hydrosphere, atmosphere, and biosphere are predicated upon distinguishing between these proposed Archean geodynamic modes. Insights into these components of the early Earth are foundational to the inner workings of terrestrial planets generally and what surface conditions and environments hosted the development of the first life.

Arguments for alternative geodynamical regimes in the Archean are often based on inferences of a regime transition toward modern-style plate tectonics. Existing estimates for the age of such a transition range from the Neoproterozoic to the Hadean (see the Supplementary Materials) and invoke a range of observations including global and local geochemical records, field relations of possible syn-tectonic rocks, and paleomagnetic pole comparisons.  

A key discriminant between stagnant- and mobile-lid regimes is the rate of horizontal motion of plates over Earth’s surface. Absolute plate velocities have typically been ~2 to 10 cm/year (extremes from 0 to 25 cm/year) over the last 400 million years (Ma), while hypothesized velocities for stagnant- and sluggish-lid models are typically less than 2 cm/year. Paleomagnetic methods may constrain the velocity of crustal blocks in deep geological time by measuring their apparent polar wander histories. However, robust paleomagnetic evidence for latitudinal motion has been lacking thus far for times before 2.8 Ga. Here, we produce a new paleomagnetic pole from ~3180 Ma volcanics in the East Pilbara Craton of Western Australia and use this result to assess the presence of plate tectonic– like processes on Earth before that time.  

Original article: Paleomagnetic evidence for modern-like plate motion velocities at 3.2 Ga. DOI: 10.1126/sciadv.aaz8670. To read the article click here.