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The permanency of position has been challenged by major theories such as continental drift theory, sea floor spreading theory and other theories of landform development. These theories help us understand the dynamic nature of Earth's surface and explain various geological phenomena observed across the globe. INITIAL OBSERVATIONS Distribution of Landmass and Water Bodies There is more concentration of landmass in the northern hemisphere (approximately 75% of landmass ) while there is more concentration of water in the southern hemisphere. Shape of Continents Except for Australia and Antarctica , most of the continents are roughly triangular in shape . Similarly, the majority of oceans are also triangular in shape . Antipodal Arrangement The triangles are arranged in such a manner that for the continents the base is to the north and apex is to the south , while for the oceans the base is to the south and apex is to the n...

What is Paleomagnetism and Geomagnetism? Complete Notes for UPSC with Wegener's Theory & Evidence Paleomagnetism and Geomagnetism Paleomagnetism and Geomagnetism deal with the study of Earth's magnetic field and the presence of magnetic direction and dip in the fossilized rocks (solid rock) because both the direction and the dip give an idea of magnetic properties of the earth as well as the drifting of the continents. Magnetic Direction in Rocks The direction of metallic minerals in the rocks reveals the direction of the magnetic field whenever the rocks were formed. Since the magnetic field keeps on shifting and the south pole of the rocks gets attracted towards the geographical North Pole , we can understand the shifting of the continents . Magnetic Dip and Intensity The dip or angle tells about the strength or the intensity of the magnetic field. Since the intensity is greatest at the poles, t...

Interior of the Earth The study of Earth's interior structure has evolved from early theories like Sir Eduard Suess's three-layer model to modern understanding based on seismic wave analysis and other scientific methods. Sir Suess proposed an early model of Earth's interior divided into three distinct layers: - SIAL - SIMA - NIFE SIAL Layer → It is dominated by Silica and Aluminium . → Average density is 2.7 gm/cm³ . → Thickness is 30 to 50 km over continent & 0 to 5 km over ocean . → Continental crust is made up of SIAL and it is dominated by Granitic rocks . SIMA → Made up of denser material, having average density of 3.0 gm/cm³ . → Heavy minerals such as iron and magnesium . → It forms oceanic crust and has dominance of Basaltic rocks . NIFE → It is most dense layer which forms core. → Average density is 11 gm/cm³ . → Domina...

Hierarchy of Landforms - Salisbury's Classification The search for geography as a systematic science resulted in simplification which in geomorphology was done by Salisbury. He classified landforms into a hierarchical order based on their scale and formation processes. SALISBURY'S CLASSIFICATION OF LANDFORMS Salisbury classified the landform into: 1. Relief Features of 1st Order This includes two major features Continental Platforms and Ocean Basins . The first order relief features are stable in the geological history of the earth, though there are some small scale changes in their forms, boundaries and geographical location. 2. 2nd Order of Relief Feature 2nd order relief features are superimposed on the 1st order relief features. Some of the examples are Mountains, Plateau, Plains on the continental landmass and mid oceanic ridges, sea-mounts are present on the ocean basins. The 2nd order relief ...

Fundamental Concepts of Geomorphology Geomorphology is the scientific study of landforms and the processes shaping the Earth’s surface, with early ideas developed by Greek and Roman geographers. ANCIENT GEOGRAPHERS Herodotus Herodotus is remembered for his geographical observation, through his statement such as "Egypt is gift of Nile" . Thus, he could attribute the erosion of river Nile in the initial stage which resulted into the deposition of silt and sediment in Egypt. Aristotle Aristotle talked about the origin of springs and explained the formation of the springs which he believed was formed due to the percolation of rainwater . Aristotle also recognised that earthquakes and volcanoes are closely related in origin. Strabo Strabo noted the changes in the landforms which was rise and fall of the sea level . He also recognised that the deltas are due to river erosion . He also wrote extensiv...