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The brittle-ductile transition zone (hereafter the "transition zone") is the zone of the Earth's crust which marks the transition from the upper, more brittle crust to the lower, more ductile crust. For quartz and feldspar-rich rocks in continental crust, the transition zone occurs at an approximate depth of 20 km (roughly equivalent to temperatures in the range 250–400°C). At this depth, rock becomes less likely to fracture, and more likely to deform ductilely by creep. This happens because the brittle strength of a material is increased by the confining pressure, whilst the ductile strength of a material decreases with increasing temperature.

Depth of the Transition Zone
The transition zone occurs at the depth in the Earth's lithosphere where the downwards increasing brittle strength equals the upwards increasing ductile strength, giving a characteristic "saw-tooth" crustal strength profile. The transition zone is, therefore, the strongest part of the crust and the depth at which most shallow earthquakes occur. The level of the transition zone depends on both strain rate and temperature gradient; the transition zone is shallower for slow deformation and/or high heat flow and deeper for fast deformation and/or low heat flow. Crustal composition and age also affect the transition zone's depth: it is shallower (~10-20 km) in warm, young crust and deeper (~20-30 km) in cool, old crust.

Changes in Physical Properties
The transition zone also marks a shift in the electrical conductivity of the crust. The upper region of the Earth's crust, which is about 10-15 km thick, is highly conductive due to electronic-conducting structures which are commonly distributed throughout this region. In contrast, the lower region of the crust is highly resistive and its electrical conductivity is determined by physical factors such as depth and temperature. Although the transition zone generally marks a shift from brittle rock to ductile rock, exceptions exist in certain conditions. If stress is applied rapidly, rock below the transition zone may fracture. Above the transition zone, if the rock may deform ductilely if pore fluids are present and stress is applied gradually.

Examples exposed on land
Sections of fault zones once active in the transition zone, and now exposed at the surface, typically have a complex overprinting of brittle and ductile rock types. Cataclasites or pseudotachylite breccias with mylonite clasts are common, as are ductilely deformed cataclasites and pseudotachylites. These sections become exposed in geologically active regions where the transition zone is located the seismic zone where most shallow earthquakes occur. A major example of this phenomenon is the Salzach‐Ennstal‐Mariazell‐Puchberg (SEMP) fault system in the Austrian Alps. Along this fault line, researchers have directly observed the structure and strength profile changes which are present in the brittle-ductile transition zone.

Original Article For Reference
The brittle-ductile transition zone is likely to be the strongest part of the Earth's crust. For quartz and feldspar rich rocks in continental crust this occurs at an approximate depth of 13–18 km (roughly equivalent to temperatures in the range 250–400 °C). At this depth rock becomes less likely to fracture, and more likely to deform ductilely by creep. This happens because the brittle strength of a material is increased by the confining pressure, whilst the ductile strength of a material decreases with increasing temperature.

The transition zone occurs at the level in the crust where the downwards increasing brittle strength equals the upwards increasing ductile strength, giving a characteristic "saw-tooth" crustal strength profile. This zone is, therefore, the strongest part of the crust and the depth at which many earthquakes occur. The level of the transition zone depends on both strain rate and temperature gradient, being shallower for slow deformation and/or high heat flow and deeper for fast deformation and/or low heat flow. Crustal composition will also affect the depth at which this zone occurs.

Sections of fault zones once active in the transition zone, and now exposed at the surface, typically have a complex overprinting of brittle and ductile rock types. Cataclasites or pseudotachylite breccias with mylonite clasts are common, as are ductilely deformed cataclasites and pseudotachylites.

Article Evaluation
Everything contained within the article is relevant to the topic in significant enough ways that they should be included. The cited information may be out of date as the newest source referenced in the article is from 2006, with the other two sources being from 2004 and 1990. Overall, the page is relatively short and could be expanded upon by more clearly explaining the idea that brittle-ductile transition zones do not occur at uniform depth and instead rely on a number of factors including material type and temperature. While the jargon is not flagrant, there are plenty of words which could be switched out to make their meanings more clear in context. The page does link to two other Wikipedia pages which are related, however, one of these two pages is not properly mentioned in the page itself and is only linked at the bottom.

The tone of the article is neutral, none of the claims seem biased towards different viewpoints as it presents facts about the brittle-ductile transition zones in a straightforward manner. Of the three sources referenced, one of the links does not work and the others are links to scientific papers. The sources seem to come form reliable, non-biased sources, however, they are both old. Being 17 and 31 years old respectively. This articles is rated as a stub and is also rated as importance level 5 to earth science. Additionally, only one person has posted a conversation topic about the article and it is a suggestion to correct the article in regards to the decrease in ductile strength with depth and temperature.