Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Phanerozoic
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present and began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons. The time span of the Phanerozoic starts with the sudden appearance of fossilized evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.
  • 5.9K
  • 08 Oct 2022
Topic Review
Lost Lands
Lost lands can be continents, islands or other regions existing during prehistory, having since disappeared as a result of catastrophic geological phenomena or slowly rising sea levels since the end of the last Ice Age. Lost lands, where they existed, are supposed to have subsided into the sea, leaving behind only a few traces or legends. The term can also be extended to mythological lands generally, to underground civilizations, or even to whole planets. The classification of lost lands as continents, islands, or other regions is in some cases subjective; for example, Atlantis is variously described as either a "lost island" or a "lost continent". Lost land theories may originate in mythology or philosophy, or in scholarly or scientific theories, such as catastrophic theories of geology.
  • 3.6K
  • 11 Oct 2022
Topic Review
The White Sea
The White Sea is a small shallow semi-closed sea in the North-West of Russia. It is strongly affected by induced tides, so the tidal motion dominates in the sea. Sea ice is seasonal and the water salinity is less than in the neighbouring Barents sea due to strong river discharge. In this entry, we focus on the sources of data on the Sea.
  • 3.4K
  • 21 Jan 2021
Topic Review
Carbonatite-Related REE Deposits
The rare earth elements (REEs) have unique and diverse properties that make them function as an “industrial vitamin” and thus, many countries consider them as strategically important resources. China, responsible for more than 60% of the world’s REE production, is one of the REE‐rich countries in the world. Most REE (especially light rare earth elements (LREE)) deposits are closely related to carbonatite in China. Such a type of deposit may also contain appreciable amounts of industrially critical metals, such as Nb, Th and Sc. According to the genesis, the carbonatite‐related REE deposits can be divided into three types: primary magmatic type, hydrothermal type and carbonatite weathering‐crust type. This paper provides an overview of the carbonatite‐related endogenetic REE deposits, i.e., primary magmatic type and hydrothermal type. The carbonatite‐related endogenetic REE deposits are mainly distributed in continental margin depression or rift belts, e.g., Bayan Obo REE‐Nb‐Fe deposit, and orogenic belts on the margin of craton such as the Miaoya Nb‐REE deposit. The genesis of carbonatite‐related endogenetic REE deposits is still debated. It is generally believed that the carbonatite magma is originated from the low‐degree partial melting of the mantle. During the evolution process, the carbonatite rocks or dykes rich in REE were formed through the immiscibility of carbonate-silicate magma and fractional crystallization of carbonate minerals from carbonatite magma. The ore‐forming elements are mainly sourced from primitive mantle, with possible contribution of crustal materials that carry a large amount of REE. In the magmatic-hydrothermal system, REEs migrate in the form of complexes, and precipitate corresponding to changes of temperature, pressure, pH and composition of the fluids. A simple magmatic evolution process cannot ensure massive enrichment of REE to economic values. Fractional crystallization of carbonate minerals and immiscibility of melts and hydrothermal fluids in the hydrothermal evolution stage play an important role in upgrading the REE mineralization. Future work of experimental petrology will be fundamental to understand the partitioning behaviors of REE in magmatic-hydrothermal system through simulation of the metallogenic geological environment. Applying “comparative metallogeny” methods to investigate both REE fertile and barren carbonatites will enhance the understanding of factors controlling the fertility.
  • 3.1K
  • 17 Nov 2020
Topic Review
Basalt
Basalt (/bəˈsɔːlt, ˈbæsɒlt, -sɔːlt/) is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows.
  • 3.1K
  • 09 Nov 2022
Topic Review
Groundwater Withdrawal-Induced Land Subsidence
Land subsidence is probably one of the most evident environmental effects of groundwater pumping. Globally, freshwater demand is the leading cause of this phenomenon. Land subsidence induced by aquifer system drainage can reach total values of up to 14.5 m. The spatial extension of this phenomenon is usually extensive and is often difficult to define clearly. Aquifer compaction contributes to many socio-economic effects and high infrastructure-related damage costs. Currently, many methods are used to analyze aquifer compaction. These include the fundamental relationship between groundwater head and groundwater flow direction, water pressure and aquifer matrix compressibility. Such solutions enable satisfactory modelling results. However, further research is needed to allow more efficient modelling of aquifer compaction. Recently, satellite radar interferometry (InSAR) has contributed to significant progress in monitoring and determining the spatio-temporal land subsidence distributions worldwide. Therefore, implementation of this approach can pave the way to the development of more efficient aquifer compaction models. This entry presents a comprehensive review of models used to predict land surface displacements caused by rock mass drainage, as well as (2) recent advances and (3) a summary of InSAR implementation over recent years to support the aquifer compaction modelling process. Therefore, the study presented would be of benefit to readers who are interested in the topic of interaction between the human population and the hydrogeological system in different regions. The research presented allows readers to better understand the factors, developments and effects of groundwater drainage and thus facilitate large - scale risk assessment and preventive planning.
  • 2.8K
  • 27 Oct 2020
Topic Review
Precambrian Supereon
The Precambrian (or Pre-Cambrian, sometimes abbreviated pЄ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian (colored green in the timeline figure) is an informal unit of geologic time, subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about 541 million years ago (Ma), when hard-shelled creatures first appeared in abundance.
  • 2.8K
  • 18 Oct 2022
Topic Review
List of Peaks by Prominence
This is a list of mountain peaks ordered by their topographic prominence.
  • 2.5K
  • 18 Oct 2022
Topic Review
Land Administration and Blockchain Technology
Transparency of processes is very crucial across all institutions. In land administration processes, this is particularly important given the multi-stakeholder involvement. This paper argues that transparency of land administration processes involves carrying out and sharing up-to-date information on ownership, value, and the use of land and all of its associated resources among related institutions, right holders and other stakeholders, including third parties, as well as, acting on the information in an open manner. To achieve this in Ghana, blockchain technology has been identified as a complementary tool to the Ghanaian land administration system. Blockchain technology refers to a fully distributed crypto-graphical system that captures and stores a consistent, immutable and linear event log of the transactions between networked actors. The study identifies that given the potentials of blockchain technology which include; decentralization of transaction to all connected stakeholders, the immutability of records, hashing of records that allows for quick access to both historical and current land transactions' data, as well as the blockchain smart contract among others, land administration processes of land tenure, land valuation, land use planning, and land development will benefit from openness, and transparency, and human error elimination. It will also eliminate fraud, and double sales of land among other land challenges identified in the Ghanaian land sector.  The study proposes that for real-time land up-date in land information across all the land sector divisions; land valuation division, land title registration, survey and mapping division, and the public and vested land management division, a permisionless public blockchain architecture be adopted for the Ghanaian land system. This is because, in comparison to the other blockchain architecture types, the permisionless public blockchain allows more transparency, decentralization, openness, integration, and also adheres to privacy and data protection laws. This study and its results are particularly important not only to the Ghanaian land sector and its stakeholders, but to all other land administration systems in the sub-Saharan Africa region given the similarities in land administration across the region. In the Ghanaian context however, the study's findings if implemented will affect the institutional relations and shared authorities between all stakeholders which include government agencies, local chiefs and individual landowners. This is because, land decisions and land data will not become shared responsibility of all stakeholders and not dependent on just some few stakeholders. A successful implementation of blockchain in Ghana's land administration will however depend on negotiations and consensus amongst the different land stakeholder, education of all stakeholders on the technology, and its impacts, as well as standardization in the land administration processes across the different land divisions. This is because, where there is no such standardization, there is a high possibility of inconsistencies and irregularities in the processes which can affect the efficient working of the blockchain system.
  • 2.2K
  • 07 Jun 2021
Topic Review
List of Minerals L (Complete)
This list includes those recognised minerals beginning with the letter L. The International Mineralogical Association is the international group that recognises new minerals and new mineral names, however minerals discovered before 1959 did not go through the official naming procedure, although some minerals published previously have been either confirmed or discredited since that date. This list contains a mixture of mineral names that have been approved since 1959 and those mineral names believed to still refer to valid mineral species (these are called "grandfathered" species). The list is divided into groups: The data was exported from mindat.org on 29 April 2005; updated up to 'IMA2018'. The minerals are sorted by name, followed by the structural group (rruff.info/ima and ima-cnmnc by mineralienatlas.de, mainly) or chemical class (mindat.org and basics), the year of publication (if it's before of an IMA approval procedure), the IMA approval and the Nickel–Strunz code. The first link is to mindat.org, the second link is to webmineral.com, and the third is to the Handbook of Mineralogy (Mineralogical Society of America).
  • 2.1K
  • 05 Nov 2022
  • Page
  • of
  • 12
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
Feedback