River Deep - Mountain High Trivia Quiz

Answer: Shield volcano

As their name implies, stratovolcanoes, or composite volcanoes, are built up by many layers of hardened lava and tephra (fragmented volcanic material), which account for their distinctive profile. This structure is due to the high viscosity of the lava, which cools and hardens quickly instead of spreading out. Shield volcanoes, on the other hand, are formed by the eruption of low-viscosity lava, which is able to travel for longer distances before cooling down in broad sheets - whose accumulation results in a low, gently sloping shape, similar to a shield lying on the ground.

While stratovolcanoes are associated with explosive activity, shield volcanoes are the product of effusive eruptions. Active shield volcanoes, such as those found in Hawaii - part of the world's largest chain of shield volcanoes, the Hawaiian-Emperor seamount chain in the Pacific Ocean - are almost constantly active. The gradual buildup of lava often creates extremely large volcanoes in terms of width: such is the case of Mauna Loa, on the island of Hawaii, which is over 100 km (60 mi) wide at its base. In addition, Mauna Loa is so massive that it depresses the crust beneath it by 8 km (5 mi) - meaning that the mountain's total height is about twice that of Mount Everest. Shield volcanoes do not only occur on Earth: Olympus Mons, the tallest known mountain in the Solar System, is a shield volcano.

Other forms of volcanic mountains are cinder cones (hills created by loose pyroclastic fragments around volcanic vents) and lava domes (mound-shaped protrusions of viscous lava). The term "shield volcano" is a literal translation of the German "Schildvulkan", coined by Austrian geologist Eduard Suess in 1888.

This burning question was written by LadyNym of the Phoenix Rising team.

Answer: True

Many mountains are created at convergent plate boundaries in the earth's upper mantle. As two plates come together, there is friction or pressure along the plate edges as they shift and slide against one another. Fold mountains are formed when plates push up against one another so that the Earth's crust (on top of the mantle) folds. It can also bend or warp. Over many thousands or even millions of years, large, sharp or rippling mountain ranges are formed. Fold mountains include some of the most famous mountain ranges on the planet, including the European Alps and the Andes Mountains of South America, created where the Nazca plate and South American plates meet. In the same way, the Himalayan Mountains formed where the Indian plate meets the Eurasian plate. The Appalachian Mountains in the eastern USA are fold mountains, and were once taller than any other mountain range, but they have been eroded with time.

This question sort of folded its way into the quiz by Phoenix Rising team member 1nn1.

Answer: Horst

'Horst' and 'Graben' are the blocks lying between fault lines that are alternately lifted (Horst) or sunk (Graben) by endogenic (internal) pressures within the earth. A Horst is also called a 'block mountain'. These are not typically as spectacular as fold mountains such as the Andes or Himalayas but may contain flat tops and steep sides. Examples include the Harz mountains in Germany and Jura mountains along the Swiss-French border. The Tamar valley in northern Tasmania is a Graben, originating from continental movements associated with the separation of Gondwanaland.

The highs and lows of this question were mapped into this quiz by PR members LadyNym and MikeMaster99.

Answer: Large particles, driven by water flow, rolling along the river bed dislodging other particles

'Saltation' has nothing to do with dissolved salts such as sodium chloride! Although there is some variation in the online etymologies, there is agreement that saltation comes from the Latin 'saltus', meaning to leap. During high flow events after heavy rains, dam releases or snow melt, the strong current causes small particles to become suspended in the water column, making the water look cloudy or 'dirty'. Larger particles are too heavy to be suspended; instead, they roll downhill like bowling balls, dislodging and moving other particles they crash into. This is saltation. Water velocities of 1 m/s (3 ft/s) will move large gravel and cobbles; larger particles require even more stream power (water velocity) to move. When water velocity slows, these larger particles stop moving and eventually much of the suspended load settles to the bottom too.

This question was rapidly inserted into the quiz stream by MikeMaster99 who takes his water chemistry class out to measure these processes.

Answer: All have brackish water

All five waterbodies are estuaries: "partially enclosed body of water with one or more rivers opening into it with an open or free connection to the open sea". As they contain fresh water from the rivers flowing in and saline water from the open ocean, the mixing zone (the estuary) has water of variable and intermediate salinities, known as brackish water. Estuaries have ocean influences from tides and waves and fluvial characteristics such as terrestrially-derived sediment and fresh water. Bays, harbours, lagoons, inlets, and sounds are usually estuaries. The East River in New York is a misnomer as it is actually an estuary.

This question flowed into the quiz by Phoenix Rising team member 1nn1.

Answer: Terminal moraine

As a glacier moves down a valley driven by gravity, it carves out rocks and unconsolidated material, rather like a bulldozer. This rock material is either pushed out to the side, forming lateral moraines, or pushed ahead of the glacier front. After the glacier reaches its most downslope extent and then starts retreating, it leaves a wall of rock debris behind. This is known as the terminal moraine. This terminal moraine then greatly impedes melt water flow thereby creating a lake. The iconic view across the turquoise waters of Lake Louise take in the towering Mt Lefroy and the Victoria Glacier. The turquoise color arises from very fine, suspended glacial till (silt) which in turn originated from the glacier's actions eroding the surrounding rock.

This question brought back great memories for PR member MikeMaster99, who visited this lake many times (in all seasons) while living in Calgary.

Answer: Lake Taupo

A rift valley is a linear depression between highlands or mountain ranges, caused by the pulling apart of the lithosphere (the Earth's crust) - an example of extensional tectonics. Many extensive rifts occur under sea level due to the spreading of the sea floor; when they occur above ground, rift lakes may form if part of a rift fills with water.

Many of the world's largest and deepest lakes are found in rift valleys - as is the case of Lake Baikal in southern Siberia, the world's largest freshwater lake by volume. Lake Superior, the world's largest freshwater lake by surface, occupies a basin created by the Midcontinent Rift of North America - which, unlike the Baikal Rift, is no longer active. The East African Rift (also still active) contains the largest grouping of rift lakes, including Africa's deepest lake, Lake Tanganyika.

Lake Taupo, located in the North Island of New Zealand, and the country's largest lake, was created by the eruption of the Taupo volcano - the largest-known eruption in the past 70,000 years, which occurred about 25,600 years ago.

This question was compiled by LadyNym of the Phoenix Rising team after some deep thought.

Answer: Wind moving sand between dunes

From Greek mythology, Aeolos (with various spellings) was the divine keeper of the winds. The Aeolian harp is a stringed instrument 'played' by the wind. Similarly, an Aeolian lake is formed by wind action scouring areas between sand dunes which then fill up with water. Many such lakes are intermittent or ephemeral, filling with water only during large storms and then evaporating to (near) dryness, often for months or even years at a time. Examples include Moses and Mono Lakes on the west coast of the USA and many ephemeral lakes in central Australia.

This question was blown into the quiz by PR member and aquatic scientist, MikeMaster99.

Answer: Billabong

An oxbow lake is a U-shaped lake that forms when a wide meander of a river is replaced by a more direct route to a downstream part of the river, which in time creates a free-standing body of water near the river. The entrance to the 'orphan' meander silts up. Eventually as they are still water lakes (no current), the lake silts up entirely, becoming swampy before complete evaporation may occur. A billabong is an Australian aboriginal word popularised in "Waltzing Matilda". In Texas, oxbows created by the Rio Grande are called resacas. In some states of the USA oxbows and cut-offs have created problems where a river forms state boundaries. If an oxbow is formed along that river, the boundary no longer follows the new river channel. An example is small sections of the Arkansas-Mississippi border, as the Mississippi River channel itself moves (meanders) across the flood plain over time.

This question sort of meandered its way into the quiz by Phoenix Rising team member 1nn1.

Answer: Man-made lakes

These three lakes were created by damming the Zambezi, Nile and Volta rivers respectively. Lake Volta in Ghana, formed when the Akosombo Dam was constructed in the 1960s, is the largest artificial (man-made) lake in the world based on surface area (3,283 square miles, 8,502 square km) but not volume. Nearly 80,000 people had to be resettled as the dam filled. The honor for the largest man-made lake by volume belongs to Lake Kariba on the Zambia-Zimbabwe border, formed when the Zambezi River was dammed in the Kariba gorge, around 400 km (250 miles) downstream from Victoria Falls. At full capacity, this lake, which opened in 1959, holds 181 cubic km (43 cubic miles) of water. To put that volume into another 'unit', this is approximately equivalent to 70 million Olympic size swimming pools. Also built in the 1960s, Lake Nasser was formed by construction of the Aswan High Dam. It was designed to serve three major purposes: the generation of a reliable hydro-electricity supply for Egypt, flood regulation and as a freshwater supply for agriculture.

This question was constructed, hopefully soundly, by aquatic scientist MikeMaster99, who continues to study impacts of dams on riverine ecosystems.