Outcrop in the context of Earth's core

The Acropolis of Athens (Ancient Greek: ἡ Ἀκρόπολις τῶν Ἀθηνῶν, romanized: hē Akropolis tōn Athēnōn; Modern Greek: Ακρόπολη Αθηνών, romanized: Akrópoli Athinón) is an ancient citadel located on a rocky outcrop above the city of Athens, Greece, and contains the remains of several ancient buildings of great architectural and historical significance, the most famous being the Parthenon. The word Acropolis is from Greek ἄκρον (akron) 'highest point, extremity' and πόλις (polis) 'city'. The term acropolis is generic and there are many other acropoleis in Greece. During ancient times the Acropolis of Athens was also more properly known as Cecropia, after the legendary serpent-man Cecrops, the supposed first Athenian king.

While there is evidence that the hill was inhabited as early as the 4th millennium BC, it was Pericles (c. 495–429 BC) in the fifth century BC who coordinated the construction of the buildings whose present remains are the site's most important ones, including the Parthenon, the Propylaea, the Erechtheion and the Temple of Athena Nike. The Parthenon and the other buildings were seriously damaged during the 1687 siege by the Venetians during the Morean War when gunpowder being stored by the Turkish rulers in the Parthenon was hit by a Venetian bombardment and exploded.

Pedra Branca (European Portuguese: [ˈpɛðɾɐ ˈβɾɐ̃kɐ]), also known as Batu Putih (Malay: [batu puteh]), is an outlying island and the easternmost point of Singapore. The name of the island, which is Portuguese for "white rock", refers to whitish guano deposited on the rock. The island consists of a small outcrop of granite rocks with an area of about 8,560 square metres (92,100 sq ft) at low tide. During the low water spring tide it measures, at its longest, 137 metres (449 ft) and has an average width of 60 metres (200 ft). Pedra Branca is situated at 1°19′48″N 104°24′27″E / 1.33000°N 104.40750°E / 1.33000; 104.40750, where the Singapore Strait meets the South China Sea, and so is considered a maritime landmark of the eastern entrance of the Singapore Strait.

There are two maritime features near Pedra Branca. Middle Rocks, under the sovereignty of Malaysia, consists of two clusters of small rocks about 250 metres (820 ft) apart situated 0.6 nautical miles (1.1 km; 0.7 mi) south of Pedra Branca. South Ledge, which is 2.2 nautical miles (4.1 km; 2.5 mi) to the south-south-west of Pedra Branca, is a rock formation visible only at low-tide.

The internal structure of Earth is the layers of the planet Earth, excluding its atmosphere and hydrosphere. The structure consists of an outer silicate solid crust, a highly viscous asthenosphere, and solid mantle, a liquid outer core whose flow generates the Earth's magnetic field, and a solid inner core.

Scientific understanding of the internal structure of Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through Earth, measurements of the gravitational and magnetic fields of Earth, and experiments with crystalline solids at pressures and temperatures characteristic of Earth's deep interior.

The Dresser Formation is a Paleoarchean geologic formation that outcrops as a generally circular ring of hills in the North Pole Dome area of the East Pilbara Terrane of the Pilbara Craton of Western Australia. This formation is one of many formations that comprise the Warrawoona Group, which is the lowermost of four groups that comprise the Pilbara Supergroup. The Dresser Formation is part of the Panorama greenstone belt that surrounds and outcrops around the intrusive North Pole Monzogranite. Dresser Formation consists of metamorphosed, blue, black, and white bedded chert; pillow basalt; carbonate rocks; minor felsic volcaniclastic sandstone and conglomerate; hydrothermal barite; evaporites; and stromatolites. The lowermost of three stratigraphic units that comprise the Dresser Formation contains some of the Earth's earliest commonly accepted evidence of life such as morphologically diverse stromatolites, microbially induced sedimentary structures, putative organic microfossils, and biologically fractionated carbon and sulfur isotopic data.

In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover".

Basement rock consists of continental crustal rock which has been modified several times through tectonic events including deformation, metamorphism, deposition, partial melting and magmatism.

Methane clathrate (CH₄·5.75H₂O) or (4CH₄·23H₂O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice. Originally thought to occur only in the outer regions of the Solar System, where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of the Earth (around 1100 m below the sea level). Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.

Methane clathrates are common constituents of the shallow marine geosphere and they occur in deep sedimentary structures and form outcrops on the ocean floor. Methane hydrates are believed to form by the precipitation or crystallisation of methane migrating from deep along geological faults. Precipitation occurs when the methane comes in contact with water within the sea bed subject to temperature and pressure. In 2008, research on Antarctic Vostok Station and EPICA Dome C ice cores revealed that methane clathrates were also present in deep Antarctic ice cores and record a history of atmospheric methane concentrations, dating to 800,000 years ago. The ice-core methane clathrate record is a primary source of data for global warming research, along with oxygen and carbon dioxide.

The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lithology may refer to either a detailed description of these characteristics, or a summary of the gross physical character of a rock. Examples of lithologies in the second sense include sandstone, slate, basalt, or limestone.

Lithology is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. In certain applications, such as site investigations, lithology is described using a standard terminology such as in the European geotechnical standard Eurocode 7.

Long Ya Men or Longyamen (simplified Chinese: 龙牙门; traditional Chinese: 龍牙門; pinyin: lóngyámén; Malay: Batu Berlayar) or Dragon's Teeth Gate, is the name that Chinese explorer Wang Dayuan recorded for Batu Belayar, a craggy granite outcrop that formerly stood at the gateway to Keppel Harbour in Singapore. In his description, "The strait runs between the two hills of the Temasek (Chinese: 單馬錫; pinyin: Dānmǎxī; Pe̍h-ōe-jī: Tan-má-sek or Chinese: 淡馬錫; pinyin: Dànmǎxī; Pe̍h-ōe-jī: Tām-má-sek) natives which looked like a dragon's teeth." From there, the name Long Ya Men or Dragon Teeth's Gate was born.

The rocky outcrop served as a navigational aid to ancient mariners sailing through the swift waters of the narrow channel, but was subsequently destroyed by the British in 1848 to widen the channel for larger vessels to sail through. In 2005, a symbolic replica was erected by the Singapore government near its original site to mark the role it played in Singapore's maritime history.

In geology, texture or rock microstructure refers to the relationship between the materials of which a rock is composed. The broadest textural classes are crystalline (in which the components are intergrown and interlocking crystals), fragmental (in which there is an accumulation of fragments by some physical process), aphanitic (in which crystals are not visible to the unaided eye), and glassy (in which the particles are too small to be seen and amorphously arranged). The geometric aspects and relations amongst the component particles or crystals are referred to as the crystallographic texture or preferred orientation. Textures can be quantified in many ways. A common parameter is the crystal size distribution. This creates the physical appearance or character of a rock, such as grain size, shape, arrangement, and other properties, at both the visible and microscopic scale.

Textures are penetrative fabrics of rocks; they occur throughout the entirety of the rock mass on microscopic, hand-sized specimen, and often outcrop scales. This is similar in many ways to foliations, except a texture does not necessarily carry structural information in terms of deformation events and orientation information. Structures occur on a hand-sized specimen scale and above.

The Eagle Ford Group (also called the Eagle Ford Shale) is a sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas. The Eagle Ford is predominantly composed of organic matter-rich fossiliferous marine shales and marls with interbedded thin limestones. It derives its name from outcrops on the banks of the West Fork of the Trinity River near the old community of Eagle Ford, which is now a neighborhood within the city of Dallas. The Eagle Ford outcrop belt trends from the Oklahoma-Texas border southward to San Antonio, westward to the Rio Grande, Big Bend National Park, and the Quitman Mountains of West Texas. It also occurs in the subsurface of East Texas and South Texas, where it is the source rock for oil found in the Woodbine, Austin Chalk, and the Buda Limestone, and is produced unconventionally in South Texas and the "Eaglebine" play of East Texas.

The Eagle Ford was one of the most actively drilled targets for unconventional oil and gas in the United States in 2010, but its output had dropped sharply by 2015. By the summer of 2016, Eagle Ford spending had dropped by two-thirds from $30 billion in 2014 to $10 billion, according to an analysis from the research firm Wood Mackenzie. This strike has been the hardest hit of any oil fields in the world. As of 2016, the spending was, however, expected to increase to $11.6 billion in 2017. A full recovery was not expected any time soon.

The Dnieper rapids (Ukrainian: Дніпрові пороги, romanized: Dniprovi porohy) also known as cataracts of the Dnieper, were the historical rapids on the Dnieper river in Ukraine, caused by outcrops of granites, gneisses and other types of bedrock of the Ukrainian Shield. The rapids began below the present-day city of Dnipro (formerly Kodak Fortress, Yekaterinoslav), where the river turns to the south, and dropped 50 meters in 66 kilometers, ending before the present-day city of Zaporizhzhia (whose name literally means "beyond the rapids").

There were nine major rapids (some sources give a smaller number), about 30–40 smaller rapids and 60 islands and islets. The rapids almost totally obstructed the navigation of the river.

The Lewisian complex or Lewisian gneiss is a suite of Precambrian metamorphic rocks that outcrop in the northwestern part of Scotland, forming part of the Hebridean terrane and the North Atlantic Craton. These rocks are of Archaean and Paleoproterozoic age, ranging from 3.0 to 1.7 billion years (Ga). They form the basement on which the Stoer Group, Wester Ross Supergroup and probably the Loch Ness Supergroup sediments were deposited. The Lewisian consists mainly of granitic gneisses with a minor amount of supracrustal rocks. Rocks of the Lewisian complex were caught up in the Caledonian orogeny, appearing in the hanging walls of many of the thrust faults formed during the late stages of this tectonic event.

A rock formation is an isolated, scenic, or spectacular surface rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock. The term rock formation can also refer to specific sedimentary strata or other rock unit in stratigraphic and petrologic studies.

A rock structure can be created in any rock type or combination:

Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classification of rocks is based on the information acquired during the petrographic analysis. Petrographic descriptions start with the field notes at the outcrop and include macroscopic description of hand-sized specimens. The most important petrographer's tool is the petrographic microscope. The detailed analysis of minerals by optical mineralogy in thin section and the micro-texture and structure are critical to understanding the origin of the rock.

Electron microprobe or atom probe tomography analysis of individual grains as well as whole rock chemical analysis by atomic absorption, X-ray fluorescence, and laser-induced breakdown spectroscopy are used in a modern petrographic lab. Individual mineral grains from a rock sample may also be analyzed by X-ray diffraction when optical means are insufficient. Analysis of microscopic fluid inclusions within mineral grains with a heating stage on a petrographic microscope provides clues to the temperature and pressure conditions existent during the mineral formation.