Laki or Lakagígar is a volcanic fissure

Fissure vent

A fissure vent, also known as a volcanic fissure or simply fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels...

 situated in the south of Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

, not far from the canyon of Eldgjá

Eldgjá

Eldgjá is a volcanic canyon in Iceland. Eldgjá and the Katla volcano are part of the same volcanic system in the south of the country. Eldgjá means "fire canyon" in Icelandic....

 and the small village Kirkjubæjarklaustur

Kirkjubæjarklaustur

The village Kirkjubæjarklaustur is a village in the south of Iceland on the hringvegur between Vík í Mýrdal and Höfn. It is part of the municipality of Skaftárhreppur with approximately 120 inhabitants.-Location:...

, in South-East Iceland.
Lakagígar is the correct name as the Laki mountain itself did not erupt, but fissures opened up on each side of it.
Lakagígar is part of a volcanic system, centering on the Grímsvötn

Grímsvötn

The Grímsvötn sub-glacial lakes and the volcano of the same name are in South-East Iceland. They are in the highlands of Iceland at the northwestern side of the Vatnajökull ice-cap. The lakes are at , at an elevation of...

 volcano and including the Þórðarhyrna

Thordarhyrna

Þórðarhyrna is one of seven subglacial volcanos beneath the Vatnajokull glacier Iceland.-Eruptions:It last erupted in 1910 and prior to that in 1903...

 volcano. It lies between the glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

s of Mýrdalsjökull

Mýrdalsjökull

Mýrdalsjökull mire dale glacier" or " mire valley glacier") is a glacier in the south of Iceland. It is situated to the north of Vík í Mýrdal and to the east of the smaller glacier Eyjafjallajökull. Between these two glaciers is Fimmvörðuháls pass. Its peak reaches in height and in 1980 it covered...

 and Vatnajökull

Vatnajökull

Vatnajökull is the largest glacier in Iceland. It is located in the south-east of the island, covering more than 8% of the country.-Size:With an area of 8,100 km², Vatnajökull is the largest ice cap in Europe by volume and the second largest in area Vatnajökull is the largest glacier in...

, in an area of fissures which run in a south-west to north-east direction.

The system erupted over an 8 month period during 1783-1784 from the Laki fissure and the adjoining Grímsvötn volcano, pouring out an estimated 14 km³ (3.4 cu mi) of basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 lava and clouds of poisonous hydrofluoric acid

Hydrofluoric acid

Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....

/sulfur-dioxide compounds that killed over 50% of Iceland's livestock population, leading to famine which killed approximately 25% of the population.

The Laki eruption and its aftermath has been estimated to have killed over six million people globally, making it the deadliest volcanic eruption in historical times.