"There is something going on out there, going on on the street level that will lead to a big explosion."

The "something" that black Catholic laywoman Emily Lewis perceived going on in her native Los Angeles brought her here last week to a two-day consultation on tensions between blacks and Hispanics.

The sociology experts at the conference, sponsored by the National Catholic Conference on Interracial Justice, were able to offer evidence for the validity of the fears of Lewis and more than 40 other participants. But cures for the social ills were harder to find.

"It's there, it's real and it's potentially dangerous," said Dr. Rodolfo Alvarez, professor of sociology at the University of California at Los Angeles. "Given the state of the economy and things like the resurgence of the Ku Klux Klan . . . you could easily have a flash point in California, and God help us if we do, because it's bigger than Miami and there's a lot more armament."

But as Alvarez and others made clear, competition and tensions between blacks and Hispanics, the two largest minority groups in the country, is by no means restricted to California.

Dr. Jacquelyne Jackson, a Duke University sociologist, tended to see the conflict largely in economic terms. To her, the Spanish-speaking newcomers to this country are the nub of the problem. Jackson said that solid research data are lacking on the impact of illegal aliens on the black community and that "the absence of data leads to increased emotionalism around the problem."

Nevertheless, Jackson, a former professor at Howard University, said that poor blacks are being deprived of both jobs and government aid because of the influx of illegal immigrants.

"Immigrant families where both the husband and wife are foreign-born receive more government services than the native born," the sociologist said.

She said she opposes illegal immigration and advocates a tighter enforcement of immigration laws. "We can't neglect our native born . . . to help foreigners," she said.

Brother Cyprian Rowe, head of the National Office for Black Catholics, disputed Jackson's analysis. "I don't agree that we'd spend the money on native families if we didn't have the illegal immigrants," he said.

Several in the group objected to the term "illegal immigrant." "I prefer to call them undocumented," said one man.

Sister Rose Salazar of the United States Catholic Conference's Hispanic affairs office proposed that the basis of discussion be moved "from the question of the illegals causing the problem to [a consideration of] the circumstances causing them to come here."

In his presentation, Alvarez rejected Jackson's analysis. "We are in a growing, open system" economically, Alvarez said, "not a closed system. The economy we have today can accommodate a far greater population" than the present one. But later he said that a severe recession could change the picture.

Alvarez detailed some statistics and trends that will affect the relationships of the black and Hispanie minorities within the predominantly white culture:

The Hispanic population is generally younger, and with more women of childbearing age; the white population is "not reproducing itself from birth," he said, although there is some growth due to immigration.

Though the situation of Hispanics may vary with their country of origin, length of time in this country and the circumstances that brought them here, there is an increasing heterogeneity within the Hispanic community.

Until recently the black population was "far larger than the Hispanic." Between 1985 and 1995, the Hispanics will outnumber the black population, a development that Alvarez said "will have political consequences."

Both blacks and Hispanics are less well off than the general population, but when blacks and Hispanics have similar levels of education, Hispanics tend to make more money. Hispanics who have immigrated from South America receive pay scales "closer to whites," the sociologist said.

Blacks have more group self-consciousness than Hispanics; among older blacks, there is a higher percentage of wealthy and formally educated than among Mexican Americans.

Blacks have more special-interest organizations than Hispanics; a 1970 study revealed more than 200 black colleges but not one comparable institution for Hispanics. These colleges have "created an intellectual elite that has fostered and multiplied the leadership component for black people," he said.

Blacks have tended to develop leadership and group consciousness within their own churches -- which have been largely Protestant. Hispanics, overwhelmingly Catholic, "depend on their priests, which come mostly from O'Brien-land," said Alvarez.

Skin color tends to confuse the picture, particularly for Hispanics, since many dark-skinned Hispanics are classified in census and other data as blacks. But generally, Alvarez said, "the skin color gets lighter as you go up the politico-socio order."

The Rev. Joseph Fitzpatrick, a Jesuit sociologist from Fordham who is an expert on Puerto Rican communities, said that "the next century is going to be the Hispanic century in the U.S. Catholic Church. What this century has been in terms of European migrants in the church, the next century will be for the Hispanic."

Alvarez said that, if he were black, "I would have had a tremendous sense of fear running through my nervous system" when he heard that statement. "Here the black movement is beginning to get a piece of the action in the church in this century. Now another group is coming and they [blacks] are going to get bypassed."

The Rev. Frederick Hinton, who heads the National Catholic Conference for Interracial Justice, said he was "somewhat disappointed" that more bishops of the Catholic Church in this country did not send representatives to the conference. He estimated that about 10 or 12 dioceses were represented.

But some of the participants who did come went away almost as troubled as they came. "I learned a lot from some of the speakers," said a Washington woman who asked not to be identified, "but what can you do about it? We're going away without any coalitions formed, any organizations. What can you do?"